Originally Posted by finagle69

You're correct in that the higher number refers to the mounting pad being further from the hub-face, but what this means is that the meat of the wheel and tire is sunken more into the car, or closer to centerline. Thus, a very high (positive) offset would require spacers to kick the wheel out more. A very low offset - low positive or even negative - would tend to have the meat of the tire and wheel sticking out of fender.

This picture is a little better at explaining it. You just have to realize what the implication is of the changed mounting point.

http://www.stl-vettes.com/65Vette/Wheel-Tire/wheel-offset-5c.jpg