I see a mistake here , it can be either a fuel *OR* an air bleed screw , the newer carbys tend to have air bleed screws .

You can always tell by where it is located in the carby :

Intake side = air bleed screw

Engine side = fuel bleed screw .

Knowing the difference is important because they're adjusted completely reverse from one another .

An air bleed screw , when you turn it in (clockwise) richens the mixture .