Z1 Carb Lock Nut

1973 Z1 early carbs with the large drain nut on the bottom of the float bowl.
Can anyone confirm what the purpose of the long (tall) lock nut on the number 4 carb slide adjustment arm is for ?
I assume you turn the adjustment right down and lock it place with the large nut and then adjust the other three carbs to the number 4.
Couldn't see any reference to this in the Kawasaki workshop service manual though.

Yes that tall 8mm long nut with the round nipple adjuster is your base #4 carb. Not really any adjustment on this arrangement, tit of adjuster bottoms out underneath the long 8mm nut. 

I like to change them out to all adjustable. I think it makes it a bit easier to sync.

Great - thank you guys.