Last Booted

When I connect to a machine and login before opening the remote desktop it shows a bunch of stats one of them is Last Booted and shows the time in either days, hours or minutes since the laptop was last booted.  I have been talking to some users that swear they shutdown the laptop every night yet it shows Last Booted as days ago.  Does this stat only track from when the user selects reboot and doesn't update if the person selected Shutdown?  To me it seems like that should get updated to last time the computer completely shuts down and then is started again not just when restarted is selected from the Start Menu or are users just not waiting long enough for the laptop to shutdown properly?