You can carry 1000 pounds in one trip? Respect!
The truck carries 1000# in one trip - 4 jaunts to the pellet place. Of course the total 'climb' for all 4 hauls is only 4m. I figure 2m+ for each of 100 trips up and down the stairs, but only 4m registered on the Garmin.
Well, the DEM doesn't know that you have a basement, it's surprising it registered any climb at all.
And it looks like most of the climb is probably because it didn't have a good position fix to start and thought you were on the other side of the yard. :-)