Win 7 defrag 1%, Defraggler 22% Who's right?

I've let Windows 7 defrag my pc automatically one evening a week for years. It says it's 1% fragmented. But when I tried Defraggler it reports it's 22% fragmented. Why would they disagree? Either a file is fragmented or not--IMHO.

http://forum.piriform.com/index.php?showtopic=35458&view=getnewpost