KeyRocket automatically checks for an update every time it is started. This is usually when you start your PC, as KeyRocket is part of the auto-run programs.
If the check reveals that the server has an update, the newer version is downloaded to your machine.
The update is installed during the next start of KeyRocket (which is normally the next time you restart your PC).
So effectively KeyRocket needs to be restarted twice before the update is installed.