For R28 device: A user can add up to 5 cards. The user can add up to 5000, so you can add up to 25,000 cards in total. (FW:28.30.3.108)
For R29 device: A user can add up to 5 cards. The user can add up to 20,000, so you can add up to 100,000 cards in total. (FW: 29.30.2.907)