reply to callous You probably connected two different routers? Maybe recently changed / cloned a MAC address to your modem?
The "allowed" only looks at what is directly connected to the modem. It shouldn't matter what's connected after that. In other words you can have as many computers connected to the router as it can handle. However, only two different MAC addresses to the modem (ex: 2 different routers).
I believe it should reset after awhile. A power cycle for my SB6121 does the trick when I troubleshoot my routers.