Duration of time connected in vpn ?

I tried to create a table with the connected users of vpn (and login admin). But it seems that the "Disconnected" do not hit correctly. The timestamp of the connected ones is apparently right, but it seems that there are no disconnected ones (only via cli) and that they do not correlate correctly. The errors are that several connections appear and only one disconnection or a correlation that does not match correctly. 

I wish there was a panel on the fortigate showing the activity / connection times of the vpn users (if possible the accesses to the panel too). Thank you very much.