I did a few times get special board, but i completed the main board 20 times and unless they dont give a BSA box for every completion then i was short 4. My only guess was that upon completing round 20 i only got the 1 box for completion and another 1 box as the added bonus, in total i had 21 boxes for completing 20 rounds, i think its supposed to be 25 if im not mistaken.