Got 8 boards for 24-zone system.....?

I just received my shipment today after some back/forth go-rounds.   I have ordered a 24-zone system.

By my calculation I should have 4 boards.  (4 x 6 = 24).   However the shipment contains 8 boards.

Also the boxes labeled 6-zone interface have a ribbon cable and module with no power connector while the boxes labeled 6-zone expansion have a board that has a power connector on it.  (seems backwards)

Am I not understanding something basic here or is something terribly wrong?

Jon D.

Figured it out - a few weeks ago.  Didn't realize that the 6 'zones' on the one board aren't used if you're just monitoring.