VI Boost

hi, i bought a blitz super sound bov but it didnt come with the instructions. i installed it already, but i dont know how to adjust it. the person i bought it from told me i can adjust how loud i want it to sound by turning the screw on the top. i would ask him how to adjust it but i cant contact him since he is in japan now. does anyone have any experience with this bov, and can you tell me how to adjust it? i would think that if i tighten the screw, the quieter it would be, and if i loosen it, it would be much louder. is this correct? thanks a lot for looking at this and for your help