Perhaps, what lens is on your graphic?
I believe the Bolex film aperture is 10.26 by 7.49 mm giving a diagonal of around 12mm. I believe the octameter has 16mm, 25mm, 35mm, 50mm, 63mm, 75mm, 100mm and 150mm settings.
The diagonal of 4x5" film is 150mm. So the 16mm setting on the Octameter will approximate a 200mm lens on the Graphic and so on. If you get the 10mm adapter for the Octameter that will give a view of 125mm, or close enough to 135mm lens on the Graphic.