on one piece wheels the offset doesn't usually denote the dish sizes. for example look at works wheel on drift works you can get a 9.5 t7r with +38 and +12 both have the same measurements of the design face they just move the part that mounts to the hub in and out , where offset really makes a difference in dish is on 2pc wheels for example my work cr-2p you got more dish by lowering the offset which brang the whole center disk further inwards. What will give more dish/concave on a 1pc wheel will be its overall width.