Device: iPad Air
My Vault has more cards in it than my Gallery. As I understand it, that should not happen.
I had finished a scenario and had closed the game. I opened it a while later and began looking at my Gallery and my Vault to fully understand how they work.
Looking at the card counts, my vault had 899/899 while my gallery had 894/894.
I cannot find all the cards that are in my vault but not in my gallery, because when I go to the vault not all of the decks are available to me yet.
I did manage to find one card in my vault that is not in my gallery. In the 1 deck, in the allies, my vault had Aldern Foxglove while he was not in my gallery.
I also question the arithmetic for arriving at the totals. In my gallery I had 34/35 Henchmen in the 2 deck and in the 3 deck I had 17/18 in the Items. It is not possible for these numbers to total to 894/894. At best it could be 892/894.