Demand Management, Change Quantity ( modify, not just add )

I am working with importing a change to an order that is currently in E10. It seems when I change a line quantity the quantity is added to the current quantity in E10. How do I import a change? Is there a setting in the Demand Detail that should be flagged as a change?

Example: Current Quantity is 5, but I receive a change order to 7. I should be able to import 7 in the line item.

Thank you,
Tim