Powerbase Fins and fin boxes?

SO i just bought a new Silver Bullet and it has in the rear Power base fin boxes. Pick enclosed. I don't understand what they are about and how they work
I've got fins coming for the board from Murray but not sure how the boxes work. I have read back and seen a few people talk about them and i tried there website but they don't even list this style of box

Help needed please..

Never had a board in them before but looking at them they may allow you to adjust the fin position, using normal fcs fins, in the box, i.e forward in the box or towards the back

They also have the "specially designed" box to stop the fins pressing into the glass of your board, when you tighten powerbase fins they really pull down into the fin box and it can damage the bottom of your board. Ive used em in my katana and they go great but its got a super tuff plasticy bottom as opposed to glass n foam

ACtually i bought it second hand and the store guys didn't know. I was after if i set them forward or back what will the difference be? Hope that makes sense.

I would have thought forward would make it better turn but lose and back more the opposite