Webi prompt wide date range only returning partial results

I am building a webi report off of a BEx query. I have a mandatory, range selection, date prompt. When I try to run the report from dates of 2008 - 2011, it is only returning a small amount of rows from 2010, which does not match the results I got in BEx Analyzer. When I make the prompt optional and run it wide open, it brings back the correct results. I need to create a range that will work so if anyone has some insight as to how to bring back the correct amounts, I would appreciate it.

Thanks in advance.