I’m assuming that you are looking at a Resource Usage view and viewing the Assignment Units column. If not please provide additional information.
The Assignment Units field actually shows peak units, which can be misleading but that’s what is displayed. So, if a user enters 2 hours on a single day the Assignment units will equate to 25%. Project 2010 changes this and accurately provides both Peak (highest units across the assignment timeframe) and Assignment Units (Units originally assigned to the resource).