Delivery quantity is not defined for item &

What causes this issue?

A delivery line item has been selected for HPM/API processing that has
no delivery quantity as the basis for the quantity calculation.

How to fix this error?

Enter a delivery quantity for the item. If picking is required, also
enter the picking quantity. If the picking quantity is equal to the
delivery quantity, the oil quantity conversion will be triggered
automatically.

Error message extract from SAP system. Copyright SAP SE.