You may not delete sets with a leading 0 in the name

What causes this issue?

You try to delete a set whose name begins with a 0.
Sets whose names begin with 0 are sets which are allocated by SAP or
sets that are used for internal purposes.
These sets are not designed to be deleted.

System Response

The set is not deleted.

How to fix this error?

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.