You can only delete using a change number

What causes this issue?

You want to delete an allocation to a class. The classification data of
the object has been processed with a <DS:GLOS.change_number>change
number</>. This means that you can only delete the allocation if you
use a change number.

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?

Display the change overview to see all the changes that have been made
to the classification data of the object, as well as the change numbers
used. Choose one of these change numbers.

Error message extract from SAP system. Copyright SAP SE.