A SUM will include all rows. Your probably linked 2 tables which gives you 5 lines/rows per budget record.
You can fix it via a shared variable formula or a Running Total (I prefer RTs).
Since I cannot see your data or design, here is my guess for a Running Total...
Name=TotalBudget
Field to Summarize=Budget field
Type of SUmmary=SUM
Evaluate=On change of field (select the primary field identifier for your budgets)
Reset=Never
Place on report footer
Edited by DBlank - 08 Feb 2010 at 2:57pm