I don't mean to sound smart, but if you don't know what you are spending and where it's going, there is little point going through a sham process of filling out the (income & expenditure forms?) the bank has presented you with. If you don't know what's happening to your money then I guess any number is a s good as another.
The purpose behind building this budget is to help YOU manage; they're not just idle line-items picked from the sky.
You probably don't find this helpful and you're probably right.