adjusting gov arm?

[K204DR]

I know the lower nut and stud is for adjusting the gov arm up or down, but can anyone tell me what the other one does, other than "don't touch it"? that seems to be all I found when I searched before. just would like to know.

 

[Smokem]

Rack adjustment.

 

[K204DR]

Cool, thanks Smokem. Thats what I was thinking. So it tunes the rack to the foot kinda? I'm pretty sure it needs to be on a bench to mess with then probably.
If you accidentally messed with it a turn or two, would it be catastrophic? or would you even notice? don't have any plans to, just wondering.