its a bleeder and the numbers have no reference to anything
tighter (clockwise) should close the valve and result in less boost as less air is bled away from the waste gate actuator
loosening (counter clockwise) should raise boost
are you knocking ? whats the current boost level ?
do you have a scanmaster?
my advice is if you didnt know what that little thing was you arent ready to start playing with boost
make sure you have data like a scanmaster as a minimum and add to that a logger
make sure everything with the car is 100%
a real boost gauge , oil pressure watertemp and fuel pressure gauges
chip is correct for what your fuel and your intended boost
read everything you can find
a good site is
www.vortexbuicks-etc.com