97% rate using 2 Rhize cards - Failed lol

Here is a good question. If you use 4 cards, click the *100 gem retain checkbox* and fail, do all 4 cards retain? I have yet to try this and I'm not sure I'm willing to try and find out only one retains. Since none of my tickets get answered anymore, I doubt I'd ever get reimbursed in case it didn't work.

Maybe there is a multiplier and it charges 100 gems for each card used. ie: 3 cards = 300 gems to retain.
I'ts not clear about this, only saying 100 gems. Anyone try this yet?