First, turn off the courtesy light.
Second your meter was in the Amp scale, connected to the disconnected ground lead of the battery and the Negative post of the battery itself.
If you have a parasitic Drain it will show current flow.
Remove a fuse, then check the meter better or the same. Better you have found the circuit that is bugging you.
Same replace the fuse and remove another. Repeat until the meter gets better.
The reason that you turn the courtesy light off is that if you don't you will FRY the meter....If the door is opened or you open it.