Remember that a number >1 is a 'crop factor', film/sensor is smaller than 24mm 135 (a.k.a. FF) , i.e. APS-C = 1.6. Conversely, a format with a larger size has a crop factor of <1
So for any format larger than 135, simply divide the larger format dimension into 24
6x7 is 56mm, so 24/56 = the crop factor to use in the program.