The skill trick "Extreme Leap" reads:
Extreme Leap [Movement] Your extraordinary leaping ability carries you over great distances. Prerequisite: Jump 5 ranks. Benefit: If you make a horizontal jump of at least 10 feet during your turn, you can spend a swift action to move an additional 10 feet on that turn. Complete Scoundrel, p. 86
So, if a character with a movement of 40 feet takes a move action trying to leap over a chasm of 20 feet taking a 20 feet running start, does he...
a) ...have to make a Jump check DC 10 and use the skill trick "Extreme Leap" to cover the distance over the chasm and has 10 feet of movement left on the other side.
b) ...have to make a Jump check DC 20 to cover the distance and get a bonus move of 10 feet once he lands on the other side.
From the name of the trick and the phrase "your extraodinary leaping abiltiy carries you over great distances" I always assumed the trick adds another 10 feet jumping distance, but rereading the benefit text I am not sure now.