A Single-Left-Click of the Sentry system tray icon displays the Sentry Projector Timer dialog:
Simply drag the slider control until the desired time setting is attained.
If more or less time is needed, you can re-enter this dialog at any time before the timer expires and increase or decrease the time allotted.
The default maximum time allowed by the timer is 3 hours. This maximum can be changed by customizing the ProjectorPatrol.INI file.