There is a correlation between the number of active users and concurrent connections but it is not a 1:1 ratio.  Concurrent connections are the number of currently open TCP/IP connections on an agent.  Active users are the number of currently executing users on an agent.  Each virtual user can and should have more than one concurrent connection open and this is a browser setting.  If you go to SETTINGS | ACTIVE PROFILE | WEB | BROWSER in SilkPerformer you will see a list of some of the browsers SilkPerformer can emulate and each has its own predefined setting for max concurrent connections to a http 1.0 or 1.1 server. 

To conclude, the number of concurrent connections is usually greater than 1 per active virtual user and this is as expected and is defined by the browser and server type.