I guess the 295 total is just a straight sum of cards in the deck (didn't check, just assumed), but there is overlap between them and we only need to field 6 at a time max, so pendulums and such we do not need so many total. So I guess we can fit a few more cards once we turn the decks into vault and the overlaps are reduced. E.g. we can easily fit other sader decks, once we have one the difference is mostly the weapon, so we can add vampire stiletto and titan too.