Looking at the Rigger Dossier it has unarmed (rating?) at 6 though the related pool seems to be 3,
This is purely speculative on my part. If you don't have a full pound box of kosher salt to take this with, you may be better off just skipping it.
Since that rating is in the Attribute block section, and next to the Defense rating, I'm guessing that is an Unarmed Defense value rather than anything that has to do with attacking Unarmed. Kind of like an unarmed parry rating.
If it had to do with attacking, I would think it would be in the block on the second page that has the FN HAR Assault Rifle.