Partial drop shipment

Hi,

We need to setup a partial dropshipment scenario for a Cup. We created an item and performed a miscellaneous receipt of 100 qty. We have done the setup for a basic dropshipment.  Then created a sales order with 120 qty. Our requirement is to issue 100 qty from the inventory and remaining 20 as a drop shipment.  However entire 120 qty created a dropshipment.  Do we have to perform further setups to achieve the desired output.