Kyoshi is correct, its not showing how much you won but how much you have so to know how much you actually won you have to know how much you had previously and subtract that from your new total. Its a weird way of doing it but your total is whats important anyway.
As for Kyoshi's question, yes you can spend it on things, just not cards. If you look in the shop there are avatars, equipment, pets, partners, and backgrounds you can buy that all cost FM. So right now FM doesn't seem like it gets you anything meaningful gameplay wise but it can help you stand out by tricking out your avatar. If we ever get a FM card lottery like DWildStar said the japanese version has, however, that will change.
The bunnies of Lavato have special abilities, like 'Action Skill: Make Carrot Disappear.'