Kcal burned by different acctivites

how accurate is this
http://www.bodytrends.com/calcount.htm

Looks like bicycling is one of the best exercises to do, way way better then walking. But how can it burn so much? Riding a bike feels so damn easy, I always get sweaty as hell and a little out of breath but it doesnt feel like its almost twice as hard as walking :unsure:

Just from riding the bike to university and back I aparently burn around 350kcal, and it would take a hour to burn that much walking...