Garmin distance head scratcher

Set out for a 50 mile ride yesterday.  Good climbs, but an ungodly wind that when coming through the canyon at one point during a small climb slowed me to 1.7 mph and had me thinking, "Am I going to need to unclip?"  But the funky thing was the distance measurement.  The midpoint of my out-and-back ride was a steady 600' climb.  At the peak my Garmin showed me at 24.9 miles, so time to head back.  Was about 1 mile out from home when my Garmin then gave me the alert I hit 50 miles, so my ride ended up being 51 miles.  Don't care about that, but it was an out-and-back, exact same route.  Where does one pick up an extra mile in that case?

So I pulled up the data and noticed on the graph that the final climb had and asymmetrical shape to it:

The uphill part measured 2.25 miles, the same on the return was 3.05 miles - a difference of 0.8 miles on the exact same route.  I'm scratching my head as to why this would be the case.  Any Garmin gurus have a good explanation?