four of us did a ride the other day that was 100 miles long. Three of us used the Garmin Edge 530 and one person was using a Wahoo. We all have completely different figures for total ascent. For the Garmin users, one showed almost 2,000 feet, one showed about 1,200 and the other about 1,400. The Wahoo uses showed 660 feet. We were traveling a relatvily flat route and Google Maps showed total elevation as about 550. What are the Garmin devices so off???