TTP8 Protection Volume Usage discrepancy

I have my boot drive (Macintosh HD) under TTP8's Protection, alerting me to when 10% space remains. I got the alert, and expected to have to clean up. Protection reports just over 113GB remaining, though the Finder reports over 311GB remaining. Why the discrepancy? I can't have this alert on if it won't work correctly, I'll just end up ignoring it.

I've rebooted, no change. I've un-selected and re-selected the radio button. What's up? Screen shots attached. (Can't attach files for some reason, so here are links to screenshots)
www.dropbox.com/s/jgsy0zifok4ooc2/Screen....07.25%20AM.png?dl=0
www.dropbox.com/s/mtcgwg78c5mw2q1/Screen....07.45%20AM.png?dl=0
www.dropbox.com/s/38iwugpp35ry9re/Screen....12.42%20AM.png?dl=0
www.dropbox.com/s/3jcgnhswoijt0o2/Screen....12.52%20AM.png?dl=0

Thanks!