Characteristic & is too long

What causes this issue?

The value of this characteristic has a defined length of more than 30.
Here you can only use characteristics with a length of 30 or less.

The system issues an error message and will not allow you to continue with this transaction until the error is resolved.

System Response

How to fix this error?

Change the defined length of the characterstic value, or use a
different characteristic.

Error message extract from SAP system. Copyright SAP SE.