98 Speedo

Just getting started with this program, so I thought I would adjust my speedo. On the 98's, it lists the parameter as tires/gears. The current program has a number of 7.29. If you take 245/50 16 diameter and divide it by 3.42 you get 7.49, not 7.29. I wanted to change the number since I have 255/50 16s on the back, but I dont understand where the 7.29 came from. The car still has original gears and has always had 245/50 16s on it.

Anyone have a clue?

as long as you change the number by the ratio of the new tire or new gear then it will be ok.