Netmaster does not supply this information out of the box.
Using NTS, you can go to /SNASESS within Netmaster to view a list of all sessions for a desired resource.
We do not supply any calculation as to total number of sessions or maximum number of concurrent sessions.
To obtain a snapshot with the current number of sessions, you can issue a variation of the IBM VTAM APPLS display, such as
which will supply a count at the bottom of the display.