The ability to create a formula on a report is a great feature. In this particular situation, a formula is being used to calculate percentages of each row's count against the total.
You can see that for this report's purposes, I only need to see the formula in the total column. It would be ideal if formulas were taken a step further and users were provided with the ability to choose which section the formula is displayed in. That way, there wouldn't be a blank formula column in each grouping and the formula would just be displayed in the total section.