offset

I think that my offset is 40 but i am not sure i have a five spoke wheel and it says 40 and 17*7jj thats it. Dose that mean that my offset is 40 and how do you change it meaning in getting it at a higher set. Also do this mean that my tire will never rub agian, and do all 17 rub with 1.5 drop rub. It only happens on really sharp short turns (like u turns).