Object & - characteristic &: value "&" does not exist

What causes this issue?

The value you entered is not defined as an allowed value for the
characteristic.
If you want to restrict the allowed values of a characteristic, the
restricted allowed values must be within the range defined.

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?

Correct the value.
Restrict the values by selecting from the allowed values.

Procedure for System Administrators

Error message extract from SAP system. Copyright SAP SE.