Time Allowance: How is it measured? Time loged in? Or time actually in use?

I am looking at setting up the Time Allowance feature within Family Safety in Windows 8 and just wondering how the hours allotted are measured.  Is it total time that the user is logged in, or time that they are actually using the PC?  For example, my kids never really log out.  They just walk away and leave themselves logged in and eventually, the screensaver will lock the screen and require their password before they can resume.  So is that time that the screen is locked, while they are signed in, counted?  Sorry if this is a dumb question....