Maybe some of the service tech members can provide a more accurate answer, but a member responded in one of my threads with this:
Response from RadarTech:
But it seems to me that you just set the bead to the rim with air, and then with the tires on the tractor and the tractor supported to take the load off the tires you rotate the tire so that the valve is at the clock position that is just past the postion would meet the 75% ratio..
Fill the tire until you think it is right, the rotate the tire to 75%, if fluid comes out your done.. If not keep adding..
Of course this could be done with the tires off the tractor too......