Double reference -> material will be ignored

What causes this issue?

You have entered both a <GL:equipment>piece of equipment</> and a
<GL:material>material</> as a reference.
You can enter <ZH>either</> a piece of equipment
<ZH>or</> a material as a reference but not both.

System Response

The system will use the piece of equipment as ther reference instead
of the material.

How to fix this error?

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.