Could you fit your measurement again? or  give your measurement data to me?

The calibration factor from count to um given by your measurement has big different from the current one (2618) as bellow;

• your factor : 1/-3563*1000 = -0.2806 um/count
• current one : 1/-1633*1000 = -0.6212 um/count

Your new factor is half smaller than the current one.