There should be an overview in the statistics/reporting section that shows for the configured intervals how you managed to work with the budgets. It should be shown how often you did not hold to the budget and how much money more/less you spent.
Additionally a sum/average over the last intervals would be interesting as It often happens that I spent too much money for a budget one month but only because I know it will be much less in the next two. It would be good to have a way to control this.

The average over the last month should also be displayed in the details of each budget. Otherwise there is no way to control, if you really should spent money.
Example: Last month I totally exceeded the budget. This month it is still "0 Euro spent". I could just start spending money. But It should show that I have to "keep calm" this month because of the last one.
Same may apply if last month nothing was spent. In this case it would be good to see that I may even go above my budget this one because I saved money the last interval.