Hi all my vendingmachines only allow to buy or sell items 1 by 1 ,, cant use the + or - keys. 
The server runs on a custom currency. Islander Token. the item has a parent item "rhib" with a skin ID. the stack for rhib on the server is set to 10000 and habdled by stackmanager.

Is there a way I can change anything so people can by or sell more items at the same time ? 

for example, you can buy a gear for 10 islander Token, but you can´t say, I buy 10 gears for 1000 tokens, because the + and - keys are disabled.

how do I fix that ?