Today I did an out-and-back run, 4 miles out and 4 miles back. I have done this exact run before with my old apple watch and many times with my newer 745 so I know it is 8 miles.
My garmin gave me a distance of 7.31 miles... even though I turned around at 4 miles and ran the same exact route back.
It also said the time was 1hr and 3 minutes to do this but during the run my watch kept reading 9:45 mile pace which doesn't make sense when doing the math. I am not sure why I an getting this in accurate tracking.