This value of 30 minutes can be changed via the -r flag. If you are accessing a website, the following a link to a different website and go back before this time limit, you are still considered as the same user. The main informaton about session found is listed. Here session really means users. The average time for one session is listed before but a histogram graph iis available.
Most people stay only a few minutes before leaving.
Longuest sessions are show. The blue line is the average. A textual table is also available if you want to get full details. You can specify some filtering to avoid a too long list to display. Here connection time should be longer than 5 minutes an the number of HTML pages should be more than 10.