Custom crafting problem

How the hell could we help you if we don't see your procedure?

You need to add an other "AND" gate to the second condition of the "OR" gate because you need to check that, if the number of items in slot 1 is not equal to 0, then it's < 64.

You need to add a new if condition to check if the number of item in slot 1 is < 63.
it gives you :
if [...] AND [(...) OR (get item from slot 1 = powder AND get item from slot 1 < 63)]