laptop issue...

heyy guys i know dis is not da place for dis topic but my issue needs to be solved...
my laptop once did not show only how much charge is remaining as in it was 85% and after one hour also showed 85%...
den i put it off after using it for 2 hours...den wen i put it on again after 1 hour it was showing 6%charge...so my issue is tat why was it showing 85%for one hour n den came bak to normal...how is it possible?