Kaseya does not detect a Windows 8.1 "Hybrid" shutdown as a reboot / shutdown.
This can lead to the "last reboot" time appearing to be incorrect.
A hybrid shutdown is not a real shutdown - it is more like hibernation, where the machine state is stored and when the machine "starts", it is returned to the previous state.
For this reason, Kaseya and also Windows does not count this as a restart.
WORKAROUND / SOLUTION
This is not a problem - this is how Hybrid shutdown works.
If you do not want to use this shutdown type, you can read the links below.
External site explaining Hybrid Shutdown - http://www.techrepublic.com/blog/windows-and-office/how-windows-8-hybrid-shutdown-fast-boot-feature-works/
Disabling Hibernation - http://support.microsoft.com/en-us/kb/920730