Android Budgets vs iPhone Budgets

I was using Monzo on iOS - the budget settings allows you to create various budgets against categories and the overall maximum spend could never be lower than the combined total of the category budgets.

I lost my iPhone and currently using the Monzo Android app and have noticed that if my combined category totals come to say £500, I can actually set my overall spend for the month to be less? Surely this is a bug or is it just different behaviour on iOS to Android?