I bought the macbook air for less than half a year, and tested the battery capacity with battery health evaluation software. It used to be 6700mah, but now it's only.

The way the battery is repaired indicates that the battery has been damaged. After the battery is used to 20%, plug in the charger and turn off the computer to charge. If you can fill it out, that's good. If it still doesn't work, you can go to the Apple Repair Center for help. This situation is basically that the battery has been damaged. If the purchase is less than one year, you can take the machine, warranty card and invoice to the maintenance station to ask for a free battery replacement.