Originally Posted by
2manybikes
Trying to get two bikes with two different bike computers, or even two car odometers to read exactly the same over a 100 miles distance is not likely to happen. It's possible but no way to really know until you try it. It may have been 100 miles.
That was my first thought, too, but the original post linked to a Garmin Connect page. Since that's based on GPS data, it's pretty accurate, and certainly not off by two and a half miles over the course of 100.