There is not a fixed relationship between the template and the number of inches that artwork will take up. That relationship depends both on the size and shape of the object that you are drawing upon.
The units on the template — pixels, not inches — relate to the motion of the motors. A full revolution of one of the motors is 3200 steps, shown on the screen as 3200 pixels, which gives 360 degrees of motion. You can think of this like latitude and longitude on a globe. 360 degrees around the equator is still one full revolution. However, the amount of distance along the equator is different on globes of different size. Similarly, lines of constant latitude are different lengths, depending on the latitude.
