After the latest update, I have more than 4 of a number of different cards. I am still unable to add more than 4 of a card to a deck, so they just sit there making me think I didn't add 4 to my deck.
The extras I have are:
6x Grave Buster
5x Mushroom Ringleader
5x Whipvine
7x Rescue Radish
5x Magnifying Grass
6x Vitamin Z
5x Kangaroo Rider
5x Cakesplosion
5x Ra Zombie
In a future update they'll add a crafting system, where you will be able to "destroy" extra cards and create cards that you don't have yet, as they say in the official website:
"There’s even more to come as we listen to your feedback, and work towards creating the best game possible by including new features and improving gameplay. Look out for additional features, including real-time competitive PvP and a crafting system, available later this year."
http://www.pvzheroes.com/news-and-media/introducing-plants-vs-zombies-heroes.html
