I found the info:

"BitCrystals, on the other hand, are divisible tokens and as stated before, are the in-game game currency for SoG, so having fractions of a whole token can be used for various things such as buying packs of cards. The cards on SoG are normally non-divisible tokens as they represent individual cards. However, to distribute FDCARDs among Folders this particular card needs to be divisible. So as long as you have one whole FDCARD in your wallet you will have the card, anything less will not be eligible to use the card in the game."

From excerpt here: http://bitcoinist.net/moonga-spells-genesis-taking-cryptocurrency-online-gaming/