Enter a valid material number

What causes this issue?

When you select a production version for a BOM using <ZK>Multiple
Selection (Active)</> option, you have entered a generic material and a
variant in the <ZK>Material</> range field. The value entered in the
lower limit must not be greater than the value entered in the upper
limit.

System Response

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

How to fix this error?

In the <ZK>Material</> field, you must enter the following values:
Only variants of a generic material (in both upper and lower limit
fields)
Only generic materials (in both upper and lower limit fields)
A generic material (in upper limit field)

Procedure for System Administrators

Error message extract from SAP system. Copyright SAP SE.