Tightening Platform Screws (M300)
In order to correct the difference in values between the center and the side calibration
points, you should tighten/loosen the two platform screws placed next to the center
point. If the center point value is 0.2 and one of the side points value is -0.2 (the
difference equals or exceeds 0.4), you should tighten the screws, whereas you should
loosen them if the center point value is -0.2 and one of the side points value is 0.2.