How to determine the concurrent users and connections connected to your firebox? The Minimum and maximum?
Concurrent connections: WSM Firebox System Manager - Front Panel - Connections
Current users: unless your users authenticate to the firewall, I am not aware of any way to know
Concurrent users would be checking the authentication list tab in Firebox System manager. If the users aren't logged in, the firewall will have no way of knowing what user is whom, and will just work off connections.
WatchGuard Customer Support