There are two parameters, full capacity and design capacity.
(Design capacity-fully charged capacity)/Design capacity is the battery loss rate.
Both the battery and the power adapter are used for power supply, you can only plug in one. But it is recommended to plug in both, which is better for the battery.
There is not much loss rate that is normal, the less the better.
How do you usually use it? Lithium batteries are most afraid of overcharging and overdischarging. If you charge the battery every time it consumes electricity, this is the method with the highest battery loss. The correct way is to charge as you use it.