Well this depends on the width of your wheel. If the wheel you're looking is 7" wide, you wanna get a higher offset. You don't necessarily get to choose the offset. I'm just referring that the wheel offset should fall somewhere in between those two numbers in order for it to fit your car with minimal to no problems.

If you're looking at the wheel from it's side, the offset would be how far the face of the wheel would stick out from the center of the wheel.