Create "Difference Total" in "Overview" panel on the right side of the screen
It would be quite lovely to have a "total difference" line item which lets you know how "on budget" you are for a given time period. The closer this number is to 0, the closer you are to being exactly on budget. The higher this number is, the more over-budget you are, etc.
Basically it would be calculated just by adding up all the "difference" columns in the budget.