I currently run 1.3.9h and have been encountering an issue with the Stock by Attribute module

I updated the stock using the “Manage Attributes Stock” tool and it is as if the website is not deducting the quantities when customers order. For example, I know I put in an accurate quantity of this product several weeks ago when we re-inventoried many of our products:

http://www.kokobeanshop.com/zebra-on...skirt-303.html

But I had a customer this week who was able to order 12 pieces in size 3-6 month (I only had 10 in stock), and the quantity in the Manage Attributes Stock function was still showing as 18 pieces after the customer placed her order. But in theory, if I put in the accurate quantity a few weeks ago, it should have been deducting as orders are placed and the customer should have only been able to order 10 pieces and the quantity should have showed as 0 (I have since removed that size option from the product since we have none left). I think there is a problem with the inventory being deducted as
customers place orders.