Clarification on EMail Bounceback Reasons

Hello - Recently CRM ODM started included specific reasons for bounces in the bounceback report.  I need some clarification on the "Bounce Reason - Specific" (last column) as they do not make sense to the marketing team pulling the Email Bounceback Reports in ODM:

Type of Bounce            Bounce Category                         Bounce Reason - Specific
Soft Bounce                  Technical/Other bounce              Other
Hard Bounce                 Hard bounce                                 User Unknown
Soft Bounce                  Block bounce                                Authentication

Thanks!