Sydney is correct.
The small trigger simply releases a catch on the mechanism that wraps (pulls) the cable up. There is no adjustment. (The thumb shifter fans will love this). However, the entire shifter may be able to be rotated forward on the plate it is mounted on. If you do not see an allen-bolt at the top of the shifter this adjustment may not be possible. And remember rotating the shifter will not change how much travel you have in the trigger util it engauges the catch mechanism.
I know the shifter is on a newer bike and that the other (left/front) shifter has a different amount of travel, but new doesn't mean pooh because it could easily be defective and comparing it to a front shifter is apples and oranges.
I would compare it to a new shifter on the same make and model of bicycle that is on the sales floor where you made your purchase. If it is as new as you say, you will be under warranty and the lbs should replace it if it proves to be a defective shifter. Careful! if you find out that the other shifter has the same amount of travel, you may find out that you just do not care for the shifters that were specified for you bike.
P.S. remember to go out and just ride the silly thing!