You've probably got too much slack in the cable in the lowest gear position. If you sit down with an allen wrench and a screwdriver and play with the cable and limit screws for a while (definitely helps to have the rear wheel off the ground) you can effectively move the shift positions around the way you want them.

You want the shifter to go fully from inner limit to outer limit with a single throw in either direction, but you'll be able to get a couple of trim positions in the middle, as well.