The system automatically adjusts the open purchase order quantity for each goods movement for the purchase order item (goods receipt, subsequent delivery, return delivery, and cancellation).
Note
At goods receipt, you must change the proposed quantity to match the quantity actually delivered. The system compares the goods receipt quantity with the open purchase order quantity and determines whether there is an underdelivery or overdelivery.
Underdelivery and Overdelivery
Default Values for Underdelivery and Overdelivery Tolerances
If the same underdelivery and overdelivery tolerances always apply for one material, you can define them in the material master record as default values for purchasing. The tolerances are determined by the purchasing value key specified in the purchasing data of the material master record.
The purchasing value key delivers the further default values and is created in Customizing for Materials Management under Purchasing→Material Master→Define Purchasing Value Keys.

If underdelivery and overdelivery tolerances that vary from the material master record are valid for a vendor-material combination, you can define the tolerances in the purchasing info record for the vendor and material.
It is also possible to specify tolerances directly in the order. The Tolerance limit for underdelivery and Tolerance limit for overdelivery fields, as well as the Unlimited overdelivery allowed indicator, are found in the detail data of an item on the Delivery tab page.