instead of overwriting the existing number with the new one, why can't you just add or subtract an amount.
If I have a random number in groceries like $457.32 and I have 32.11 available and want to add to groceries, I'd like to be able to add the 32.11 to the balance and not use a calculator first then enter the new balance. Same goes if I want to subtract small amounts from balances to move to another item, I'l like to just be able to hit a minus (-) key and type an amount to deduct, or something that is intuitive.
Thanks!