Supply Order Auto Loads one less item

[symmcom]

Hello, 

In my store i do not keep any inventory. I only order based on what customers order. So all my product Quantity is 0 at this moment. I have a customer order with 11 item. Prestashop shows i have -11 quantity for that item. When i create a supply order for that item, if i enter 0 in Automatically Load Products box, then the prestashop picks all items with 0 quantity. 

 

If i enter -1 it picks up the item i need minus 1. For example, for the item 11 quantity in need, supply order only picks 10 quantity. How can i make the supply order pick the exact quantity ordered by customer? 

Thanks!

[symmcom]

I really need this figure out. Any body any idea how to auto load exact products on the Supply Order? 

Thanks!