It gives a waring saying that the image circle will not cover the film. So,I moved the distance until it would.
Edit: The designer gave me a focal length of 50mm. I checked the distance in my plans an it comes out to 76mm. Which for 6 x 6 would be the same as 50mm on 35mm. The wizard is really confusing
for any given pinhole diameter there is a focal length, a .39 pinhole is suitable for your 76mm camera weather its 6x6, 35mm or 4x5. If you have a .3 pinhole then your correct pinhole to film plane is 45mm. As you use larger formats the light falloff at the edges is greater.