Piskie, Firstly I would like to greet you with a warm Welcome at Webhosting UK community forums
If you are still looking for getting more help on " System Usage" and want to know more about it in details then follow the steps mention below :-
Login to VZPP >> Logs >> Resources Alerts >>
you will get an
paramater tab, by clicking on it you will get all detailed information and will show you exact parameter of your VPS which are running out of resources or having any problem.
Hope this helped you !!! If you still have more questions please feel free to post.