Subprofile '&' not allowed

What causes this issue?

The sub-profile entered cannot be incorporated in the overall profile
because it does not have the same Customizing ID as the overall
profile.

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?

You can enter either:
A sub-profile that has the same Customizing ID as the overall profile
A sub-profile without a Customizing ID
You can find the possilble sub-profiles by using the F4 Help.

Procedure for System Administrators

Error message extract from SAP system. Copyright SAP SE.