Selected volume/area class is still assigned to a packaging type

What causes this issue?

The selected <DS:DE.J_7LVFLKL>volume/area class</> is still assigned to
a <DS:DE.J_7LVPART>packaging type</>.

System Response

The volume/area class cannot be deleted.

How to fix this error?

Change the assignment in the packaging type.

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.