Hi Jon,
The Unlinked attachment are the sample data from SDM $NX_ROOT\samples\data and some sample knowledge document I created.
The Unlinked attachement was unclear so I uploaded the better one and link them to the knowledge document. Afterwards I decided to do a cleanup. I did not unpublish the unwanted documents and SDM samples data. I just delete the whole Category folders. I ran all OOTB kt archive and purge rules many times. But it still shows Unlinked attachement in the repositories.
Is it some step I did that cause the Unlinked attachements still present in repositories when I did a search as screen capture in my question ?