Question on Fuel Trim calculation for PID's 6-9

Hello. I am trying to figure out which one of two formulas to calculate the Fuel trim is correct for PID’s 6-9. In various sources I find fuelTrim = (100/128)A - 100. In other sources I find fuelTrim=A/1.28 - 100. And in additional sources, I find both ways as options. Since (A/1.28)-100 is not equal to (100/128)A-100, which formula is correct? Am I missing a key piece of info here that will help me determine which formula is correct or show that both are correct? Thanks in advance for your feedback.