Credit Note does not change QTY shipped, Ordered and backorder

Hi,

We have a situation where orders need to be partially shipped from an order entry. A credit note was passed on one line item. This however did not change the quantity ordered, qty shipped to date and back ordered quantity. 

initial order 100 qty

shipped 50 qty B/O 50 qty

shipped 10 qty B/O 40

credit note passed on 10 shipped; shipped to date is still showing as 60 and B/O is 40

Please assist.