Total Time Logged In Not Matching Up With Available Licenses

I'm looking at the DateLogin and DateLogout values for users, and see that quite a few of them are showing a DateLogout value of midnight.



If the user doesnt explicitly click on the "Log Out" link in the top-right corner of the webpage, it seems the system doesnt kick them out until just after midnight.



However, even with the user technically logged in, the user doesnt seem to be taking up a license, as I see more users "logged in" than I have licenses for.



How is this possible?