Hmm, this is a first. I used Lexington, KY as the test location and the download speed of 1500 Kbps is exactly what my DSL is rated for; so, it's 100%.
I run a speed test every so often and this has never happened. I usually use a test site in Toledo, Ohio, from dslreports.com; I live in central Ohio. That location has, up to this point, given me the best results of any test sites. So, I'm skeptical about the accuracy of the above test.
From all my previous tests, 1447 Kbps download is about the best I've gotten and the results from the Toledo location are fairly consistent, usually getting 1440 - 1447 Kbps. Getting 100% is really not likely to happen unless you're very close to the nearest "central office" of your telecommunications provider. So, again, I'm skeptical about the accuracy of this test.
Edit: Cincinnati is the preferred test location for my area, per speedtest.net.