It bothers me a lot.
I charge my IPP mini-led for let’s say 20 minutes, and when I pick it up it displays the same amount of battery %.
Sometimes I restart it and it shows more %, sometimes it doesn’t.
When you have it down to a behaviour that you can reproduce I’d contact apple. I generally don’t worry about the battery unless I have a malfunctioning device that doesn’t hold a charge at all.
