battery bar on main screen slow to update?

Hi everyone, I've recently been noticing that the big battery pic (when you come out of standby) is stopping just before full, like 99%. I don't know if maybe its slow to update on how charged it is but usually the tiny little battery at the top right is full. Today the big battery froze at around 50%, but then snapped to 100 not long after. Is this a big deal or should I not worry? I remember having a laptop and the battery eventually would only charge for about 5 mins because I had plugged it in so much.

Thanks.