Classification system characteristic &3 belongs to type &4, not CHAR

What causes this issue?

You have assigned the meaning "Classification System Characteristic
&V1&" to planning characteristic &V2&. Planning characteristics that
are classification system characteristics must relate to the
characteristics (type CHAR) for the classification system. The
characteristic belonging to classification system &V3& that you entered
does in fact belong to type &V4&.

System Response

The planning scenario cannot be activated.

How to fix this error?

Define a different classification system characteristic or change the
data type for classification system characteristic &V3& to
"character-related".

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.