A relatively easy reward, because you must have been accumulated 6 seconds in the air, not in one go. After each jump you can see in the display of the show points, how long it actually was. Find a track that is packed with jumps and you'll have the reward in your pocket. In the career you will find under episode 2 with "Namibia" in Cross Country after only a few events the perfect race, which promises with the first standard car almost certainly this reward.