I wouldn't say it is unusual. The reported average is about 1% per month drop, so you are just slightly over that amount. The drop will not be linear and some months may not show a drop at all. You can expect to get the battery replaced when it drops below 80% and the cost is $99(US). All you can do is make sure to use the Optimized Charging option in the battery settings and if you charge on a regular schedule, such as every night, it will learn your behavior and only charge to 80% until just before you normally take it off the charger. If you do not charge regularly, you can use the 80% limit option where the battery health may last longer, but you will lose some use time since the battery is not at a full charge.