Water Pressure Adjustment Valve

I have a water pressure relief valve before my hose bib. when I turn the adjusting screw, which way increases water pressure and which way decreases water pressure? Also should I purchase a water pressure gauge to measure the pressure or can I determine that by the number of turns of the adjusting screw? Also would the water pressure gauge attach to the hose bib connection?
Thanks, Al

Water pressure adjustment

Buy a pressure gauge. They are less than $10.