The only way to know which setting will cut your lawn at exactly 2 inches is to try it and see. Start out at a higher setting and check the grass height after cutting a sample area. Then lower the adjusters a step at a time per the instructions in your manual until you reach the height you want. Generally speaking, the blade will not cut below the lower edge of the deck housing so a good way to get close its to put the mower on a level surface and set that lower edge to a little over your target height.
The adjustment height numbers are intended as a reference point only and do not correspond to any exact grass height. The numbers are not exact because there are are too many uncontrollable factors that could alter the overall cut height of grass. The type of grass, firmness of soil, smoothness and level of the lawn, blade type, optional tires of differing sizes, and even the speed of the engine and the speed the mower moves at all alter the cut height to some degree.