Charging indicator bug maybe?

The best practice is to plug into power whenever it’s convenient and run on battery only when you cannot connect to power. Your Mac uses Optimized Battery Charging, which is enabled by default. That is designed to charge the battery in a way that balances increased battery lifespan with your personal usage patterns. 

About battery health management in Mac laptops with Apple silicon - Apple Support

To confirm that Optimized Battery Charging is enabled, go to System Settings > Battery then click the (i) to the right of Battery Health.

If your Mac is usually plugged in, macOS will pause charging at 80% full since that’s better for the battery long term. If it was at 87% when you plug in, it will hold there for some period of time. If you frequently run on battery, macOS will charge the battery to 100%. That behavior will change depending on your usage. For example, I use my work MacBook Pro connected to a dock for most of the week, and charging pauses at 80%. If I run on battery a few hours for a couple of days, it will start charging to 100%. If I then keep the Mac plugged in for a couple of days, it will again pause at 80%. When your Mac decides to hold the battery at 80% charge, it will bring it to that level even if the battery is fully charged and the Mac is connected to power, which is what one of my Macs did here:

If charging is paused, you can override that by clicking on the Battery icon in the Menu Bar or Control Center (you may need to enable that in System Settings > Menu Bar) and select Charge to Full Now.

Once ‘trained’ the system is pretty responsive. For example, when my Mac was holding at 80%, a couple of short (30-45 minute) sessions running on battery one morning was sufficient to have macOS decide it was time to bring the battery to a full charge.

The bottom line is that your Mac will manage its battery charging to preserve the health of the battery while supporting your usage patterns. There's no need to micromanage it, let macOS handle it.

I typically use my personal Mac, a 16" M4 Pro MBP, connected to a dock, with very occasional use elsewhere in the house for a few minutes or a couple of hours. The Mac is nearly two years old, has 22 cycles on the battery and the battery health is 100%. I typically use my work Mac, a 16" M1 Pro MBP, connected to power but a few days a week I will run for a couple of hours on battery, and 1-2 times per year I will use it mostly on battery for a few days (scientific conferences). That Mac is 4.5 years old, has 221 cycles on the battery and the battery health is 91%. 

I've used Mac laptops since the PowerBook days, my experience has been that health drops from ~100% (my new Macs have mainly ranged from 98-104%, I did have one that started at 112%) to somewhere in the 88-93% range over the first 100-200 cycles (or 2-3 years, whichever comes first), then stay in that range for several hundred more cycles (or 3-4 years, whichever comes first) until they begin their inevitable decline at (with more recent Macs) between 800-1000 total cycles (or 7-8 total years, whichever comes first).

Note that there is both a usage and an absolute time component to battery longevity, even with very little actual use a battery has a finite lifespan, that's down to the chemistry in the battery that stores the power. 

harkahang wrote:

The battery percentage gets stuck at 87% and doesn't increase while the MagSafe light stays green. Restarting my Mac temporarily fixes the issue.

Try powering off the laptop while the power adapter is connected. Leave it this way overnight. If macOS is somehow interfering with the charging due to Optimized Charging, then doing this may get around this.

You can also try using a USB-C charging cable to see if that makes any difference.

Try running the Apple Diagnostics to see if any hardware issues are detected. Only a failing status is useful.

Try unplugging the power adapter from the electrical outlet for a minute in order to reset the power adapter's internal circuitry.

You can also try the troubleshooting tips in these two Apple articles (they are mostly the same, but with a few differences):

If your MagSafe cable or power adapter isn't working - Apple Support

If your USB-C power adapter isn't charging your Mac laptop - Apple Support

FYI, I have seen a few other posts on this forum where people have mentioned some odd charging issues with Golden Gate. There have not been enough reports or details to ascertain if there is any real issue with Golden Gate or if these are just a few random reports or what is unique to each system other than Golden Gate.

harkahang wrote:

The battery percentage gets stuck at 87% and doesn't increase while the MagSafe light stays green. Restarting my Mac temporarily fixes the issue.

That's normal; lithium batteries will have a much longer lifespan if they are kept between 40%-80% most of the time (there are MANY refereed papers on this in engineering and science journals and it's an intensive area of development and research for many companies). But that's on the low side for many users in a practical sense. So Apple targets something around 80%, sometimes a bit more, sometimes a bit less. But if your pattern of use involves running of the battery at certain times of day, this will be noted by the battery optimization process (optimized battery charging) in the Mac and it will try to charge to 100% right before. If you want it to charge up to something different than what you currently see, you can override the optimized battery charging and force it to charge to 100% whenever you want. However keeping it at 100% all the time will eventually mean that a replacement battery will be needed sooner. Sometimes I force mine to charge to 100% right before an airplane trip, although most planes do have some outlets available.

Maybe, maybe not.

If you think that there is a bug, send feedback to Apple.

Feedback - MacBook Air - Apple

Feedback - macOS - Apple

Otherwise, it is best to just let the MacBook Air manage the charging cycle.

Charge your Mac laptop computer - Apple Support

The battery percentage gets stuck at 87% and doesn't increase while the MagSafe light stays green. Restarting my Mac temporarily fixes the issue.