I've seen this issue pop up occasionally here, including a somewhat recent thread late last year. On that thread, a member clearly described the steps to resolve the issue. Unfortunately, I'm not having much luck locating that particular thread now. Perhaps you might find it.
In any case, I have experienced the same (or similar) issue. Apparently I fiddled with the lever a bit prior to installation, thereby losing my full range of indexing. The "fix" was simple; I needed to get the lever back to the first detent. To do this, I moved the lever to its lowest position, then removed the lever fixing bolt. I then removed the lever from the lever boss cover and repositioned it at the top position. Again, I rotated the lever down until I reached the first detent. Finally, I repositioned the lever to its correct position on the lever boss cover, secured the lever fixing bolt, and completed the install.
Note that this is how I recall resolving the problem, but I certainly didn't word this as well as others have. Also, there was no cable in the shifter at the time. The key seemed to be using the lever boss cover to reposition the lever...almost like "winding" or "unwinding" it.