How licensing utilization work in the acme sbc

Hi,

I would like to know how licensing work in terms of utilizing number of sessions?. Is there any document that I can refer to ?

We have features like below. In this case if there is a call then it will utilize only one session or two ? how about the agent registration; will it use a session as well ?

Total session capacity: 4000

Enabled features:

    2000 sessions, SIP, H323, IWF, QOS, ACP, Routing, Load Balancing,

    Accounting, High Availability, ENUM, NSEP RPH,

    IPv4-v6 Interworking, IDS, IDS Advanced, Software SRTP,

    Session Recording

Thanks,

Rajith.