You kind of got it. "Offset" is a measurement of where the hub is located from the centerline of the wheel. So, this wheel is 9" wide. Its centerline is at 4.5". However, it has a 20mm offset, which means the hub is 20mm farther away from the body of the truck. This gives it less of a lip. So, if you want a true "deep dish" look, you'd actually want a wheel with a lower offset, or even a negative offset to get the look you want. That being said, the lower the offset, the more the wheel will stick out from the body of the truck. For instance, here's an image of our 2007 F150 XLT Project truck that has 20x10 wheels with a -24mm offset. Give us a call directly at 1-877-578-2433, if you need more help. I know it gets kind of difficult to visualize.