Standard business object delegated with another standard business object

Hello All !

         I want to delegate the standard business object 2012.

         But, it was already delegated with another standard business object ADB2012 as depicted below :

         This business object is not linked with any workflow or task or not used as even as object type business object.

         According to my client requirement, the subtype business object name should begin with Z. So, I cannot use ADB2012 for creating attributes or methods. Why SAP delegates standard business object to another standard business object ? Please suggest whether I can remove this delegation.

Regards,

S.Suresh.