Found this while searching for the answer to the same question. +1 for the search function. It works.
Mine has one on top and one on bottom as well, contrary to what the manual shows.
I will take that to mean that clip in #3 or middle position and a plastic washer on either side is the stock or center position.
This is how I have been tuning it, it's nice to be sure that it's right tho'.
Great forum here tons of knowledge.