"Once you have an accurately measured place to calibrate your S625X, run that distance and make note of the distance recorded by the S625X. Your calibration factor would be
((Actual distance)/(Measured distance)) x 1000 = Calibration factor
or if you have previously calibrated your S625X, the your calibration factor would be
((Actual distance)/(Measured distance)) x (Prior calibration factor) = Calibration factor"