My battery drains a bit when it is sleeping, is this normal?

My battery was plugged in at 100%, and I closed the lid for about an hour and a half. When I came back, the battery was at 97%. Is this normal? (BTW mac is usually unplugged while in sleep mode :)

• (remaining battery capacity - 82% with 1270 cycles) (yes I know that is a lot of cycles, but I'm fine with its current capacity.)

I don't want to know what has been draining my mac while sleeping because, well, it is sleeping, not shut down, but if this type of drain is abnormal or it is draining abnormally, then I would want to know. But of course, it probably does drain the battery while sleeping.

But I just want to know if this is expected behavior and if I should be concerned.