Table is value table for clients (So not client-specific)

What causes this issue?

The table contains the client field in its first position, but is not
classified as client-specific because the table itself is defined as
the value table of the client field.
In this constellation, a table is not marked as client-specific because
this would cause meaningless classifications.
For example, this prevents tables which contain all the clients of the
system from being marked as client-specific. Such a flag would make no
sense here.

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?

Error message extract from SAP system. Copyright SAP SE.