Battery life

The absolute best way to get maximum use on a charge, as well as slow the decline of battery capacity long term is to enable Optimized Battery Charging (Settings/Battery/Battery Health) and charge the device overnight, every night. The battery will fast charge to 80%, then pause. During the nighttime pause the phone will use mains power instead of battery power, allowing the battery to “rest”, and thus reducing the need to charge the battery quite as often. The phone will resume charging to reach 100% when you are ready to use your phone; it will “learn” your usage pattern. If you enable iCloud Backup (Settings/[your name]/iCloud - iCloud Backup) the phone will back up overnight also, assuring that you can never lose more than the current day’s updates. Here's more information→About Optimized Battery Charging on your iPhone - Apple Support

It's more than okay, bearing in mind that that value is approximate and it's related to when the battery (not the iPhone) was new.

Start worrying when the maximum capacity goes down below 83-82%.

See also these useful suggestions:--> When to charge your iPhone or iPad - Apple Community

Regards

Giulio

99% is super. Normally, things will drop about 1% a month during the first year. Your battery is doing great.

No reason to stop charging the phone at 80% though, since the iPhone cannot overcharge. Make sure that the phone is set up for Optimized Battery Charging. Plug the iPhone into the charger every night before you go to bed for best chances for a long battery life.