AFE4490SPO2EVM: AFE4490 SpO2 Conversion

To my understanding, calculating SpO2 is given by the general formula of % SpO2 = 110 – 25 × R, where R = (ACrms of Red / DC of Red) / (ACrms of IR / DC of IR). I have been trying to figure out the SpO2 but have been off with the general range by an error of approximately -2. I'm wondering if the coefficients of 110 and 25 are constant as with most infrared and red sensors are if the specific module had certain calibration coefficients.