Gps-speedsurfing

How is it possible that someone has a duration of for example 2 hours, has an hour speed of 28km/h but has a total distance of 70 km?

http://www.gps-speedsurfing.com/default.aspx?mnu=user&val=118160&uid=4037

 

Just an example I have seen it more often.

 

AVANTI