You'd have to know what the percentage is a percent of - last month's hours? this month's hours?
Once you know what the percentage is a part of (a percent of) you would then figure out, for example, the 95% of the number of hours - and there you'd have a new number of hours.
If you figure out what, exactly, is the number of hours you're starting with; and if you find any percentage of those, there's no converting to be done. You have your answer in hours.