Order unit of measure &1 will be changed to unit of measure &2

What causes this issue?

A process order has been created without a material. The order quantity
is entered in a unit of measure that cannot be converted to the unit of
measure specified in the master recipe.

System Response

The system replaces the order unit of measure with the unit of measure
maintained in the recipe header.

How to fix this error?

Confirm this message. Order creation is continued with the changed unit
of measure.

Error message extract from SAP system. Copyright SAP SE.