I just plotted the route on CalTopo and got 20.12 miles and 6,902’ gain, round trip. The CalTopo route consisted of a gazillion individual points. I think that CalTopo just adds up the horizontal distance and elevation gain for each segment of the route. GPS altimeters aren’t very accurate, and barometric altimeters are even worse. I would trust CalTopo over my altimeters, so I don’t think 7,000’ is very far off.