That's common, actually. What happens is if the battery "rests" it developes a larger 'surface charge' (an apparent
potential on the contacts, that is more than it can actually supply in any real quantity). Also, the meter has pretty low resolution 25% per block, so it 'slips' around a bit on top of that. Nothing to worry about, and as long as the charge is supposed
to (and generally does) last, not really a problem.