Yes that's it, the pilot screw.
You use it to adjust the amount of fuel getting to the engine when the throttle is shut, for tickover and small throttle openings up to about 1/4 throttle.
Turn it in (clockwise) to reduce fuel & out to increase.
At 6 turns out from closed your pilot screw was doing nothing, any more than 3.5 to 4 turns out & the hole it covers is completley open, so if you need more fuel, you need a bigger pilot JET (In my previous post I said the mixture (pilot) screw had an effect through out the range, that was BOLLOCKS, it's the JET that has an effect, sorry

)
If you want, tomorrow I'll scan page 6-2 of the manual & try to expain what happens.
Rick