If the idle is increasing by only 100 rpm rather than 200 rpm, that is no big deal really, as long as the main advance function of the cold start is still working well and the car starts and idles smoothly when cold. 100 rpm should be OK.
If you want it to kick the idle speed up a little more though, all you would have to do is make a slight adjustment of the position of the ball stud on the top of the cold start lever. The same one you already were moving before, right?
It may take a few tries to get it where you want it. Idle too low is better than idle too high though. So unless it bothers you, you may wish to just leave it as is, again it will not hurt anything like this. If you do raise it, do so in very small adjustments. You don't want to have the engine racing just after a cold start, nor do you want to be having to engage the transmission with a too high idle.
Remember also you do not want to touch the cable portion of the cold start system since that is a bench calibrated adjustment that you don't want to mess with. Only do it using the position of the ball stud.
