MacBook Air (2020) discharges while shut down.
The clamshell lid seems to be fully closed while I am not using the laptop for days at a time.
MacBook Air 13″, macOS 10.15
If the laptop is shut down the battery can still drain if you're not using it
Same with my wheelchair, after charging it for a 100% it loses 10% when standing still for a day. When I had old batteries in it it would drop 40% when standing still overnight
What I want to say with this, it could just be normal battery behavior