Unless someone alters the TB idle screw, that never needs to be touched, 99% of the time. As said, the IAC controls the idle, all of the time, the idle screw is never supposed to have anything to do with the idle. If it has to be adjusted, ask the question; who messed with it, and why did they mess with it?
The throttle blade simply needs to be an amount above closed, allowing a very small amount of air in, little enough that the engine will shut down when the IAC stops helping additional air to get passed the TB blade.
I don't know the official procedure for setting the idle screw to the OEM spec position, but I have never needed to know it. I have read the steps before, and I don't recall them being exactly as described above. I think the setting should be low enough that the engine will die without the IAC providing more air, which helps to reduce dieseling or the affects of a backfire.
BTW, in contrast, I am very familiar with the adjustment of a carburetor idle screw. That is very important, and in most cases it needs to be adjusted, so that the transition fuel circuit is beginning to flow while at idle. That reduces a bog due to lack of fuel as the transition circuit tries to catch up. For a carb, the answer is to set the idle as needed, then check the transition hole or slot, and readjust the screw. Often that ends up requiring a hole(~1/8") drilled into the throttle blades, and then the screw is adjusted again, etc, until the idle is correct for the proper throttle blade position.
For an EFI, leave the idle screw alone, forever, unless it has been messed with, and only then, find the proper procedure, and correct the screw position. Then if that has to be done, never touch it again. It is not something that has to be done, or needs to be, often or every once in a while. You are messing with something that should not be, the idle control is in the computer, learn how to adjust that, and leave the idle screw alone.
