& serial numbers are already maintained. Quantity cannot be changed

What causes this issue?

The delivery quantity cannot be changed to a number lower than the
serial numbers you have already assigned.

System Response

The system rejects the change of quantity.

How to fix this error?

First delete the serial numbers that were not delivered, thereby
adjusting the number of serial numbers to match the desired delivery
quantity. Then you can reduce the delivery quantity.

Procedure for System Administrators

The system issues an error message and will not allow you to continue with this transaction until the error is resolved.

Error message extract from SAP system. Copyright SAP SE.