For Company Computer users clock out is usually last computer activity - most commonly turning off the device.
When the device is not turned off for any reason, Insightful will auto Clock Out after 4 hours of constant inactive / idle time detected by default
Clock Out timestamp will in this case be last recorded activity prior to detected inactive time.
Example: If user's last activity (any keyboard or mouse movement) was at 5 PM with computer left turned on, Insightful will Clock Out at 9 PM after 4 hours, with timestamp on the dashboard of last activity recorded (5 PM)
To change the 4 hour threshold to a different time required for this action to take effect go to Settings >> Tracking Settings >> Advanced Settings