512 max number of clients in an Unleashed network. Unleashed network supports mix model of APs (Unleashed R310, R500, 600, T300, and T301).
Even if you have R310s only in your Unleashed network it can support up to 512 clients.
At the same time, R310 supports 100 clients per AP. So, to max out the 512 clients in an Unleashed network, you would need at least 6 * R310s.