I think you've found a great feature. That's part of the distance from you circle. (Can't remember its proper name.) It should show the number of miles somewhere along the line. It shows up when you drag the map.
Interesting. When I first saw this there was no distance/time box on the line. Just a straight diagonal line which I now see is due to the scale I was using. Now there is a time/distance box every time in the middle of the line.