Hello Ramza!
I found a pretty gamebreaking bug. Your main crafting plugin makes the game only decrease one of a particular item. Even if you decreased it by 10.
Example: the player gets 50potions and later he gives 10potions to an old lady. After you handed out the potions, you can see there are 49potions in your inventory left.
I hope you get what I mean!^^ I tested it also in your sample project. Please try to reproduce the bug.