SSRS and the IN filter

So I have a SQL database with the field "reportype" which is an integer field.  In SSRS I made a parameter with multiple values and I specified the values so my users would see "budgetary" instead of "1".  After that I set a filter up where the field "proposaltype" is IN and that parameter.  Now this setup works great if I only select one item, but if I select multiple items the report only filters on the first proposaltype in numeric order.  for example if I select types 2 and 4, the report will only show type 2.   I'm new to SSRS but my TSQL mind thinks this should work.  Clearly it's not passing all the values selected, so how should I be using the IN function and what should I do to make this particular filter work?