Usually garmin connect is spot on with regard to the math, however... I just looked at my recent activity and noticed that my daily run that always measures around 4.02 mi was under-reported as 3.94. This is not much different, and initially I thought this could have been the result of GPS error, or somesuch. But then I looked at the details of the run, with the splits. It claims that 1.00 + 1.00 + 1.00 + 1.00 + 0.03 = 3.94.
Split
Time
Distance
Avg Pace
1 7:47.2 1.00 7:47
2 7:52.6 1.00 7:53
3 7:59.4 1.00 7:59
4 7:38.3 1.00 7:38
5 :13.2 0.03 7:43
Summary 30:49.0 3.94 7:49