he's rightIt depends and could be different for every game.
If you have the subtracting function, and null it (as Leiikun said) your currency won't go down. (Or change the subtraction for an addition so it goes up)
If you have the function that stores the value itself, just make it store the value you want/some big number.
You will have to test and figure out which one is the one you're looking for.