After discussing with Marco privately, we realize it is due to a recent change on both the InControl and the 6.1.2 firmware. Actually, that’s not a bug.
Since a recent InControl release, clients that are with zero bandwidth usage are not counted, regardless they are on the same or different subnet. As long as a client consumed some bandwidth, it will be counted.
Also, prior to firmware 6.1.2, if a routed client (i.e. on different subnet) is seen by the device even once, the client entry will stay in the Client List forever until the device is rebooted. Since firmware 6.1.2, idled routed clients will automatically be cleared. So you may see the no. of clients on the web admin is also dramatically smaller than before.
Hope it answers.