What is the correct calibration method to calibrate this type of depth gage (photo attached)? I was trained to zero out on surface plate than measure different sizes of gage blocks taking a low, middle and high measurements, but my gage reads in .001 and my calibration tolerance is +/-.0005. I can’t meet that with this method. Also, what if the two surfaces are not flush (see 2nd picture) Doesn’t this effect the measurement? As I learn more, I don’t think I’m getting trained right lol!