I just got a KX1 and while setting it up, in inches, because thats my native unit, I found I needed 12744 steps per in instead of the calculated 12700. I posted on the smallcncsupport site and got Adams expected posting to use metric.
Just as a test I did a metric setup and made accurate measurements and found the pitch must be 502, not the calculated 500.
The machine has a slight pitch error in the screw, it may well be within tolerance for the screw design.
Bottom line is one should measure his machine accurately and set the steps per to the measurements, not to the calculated value.
Im doing a training video for LIttleMachineShop and I will be covering this is some detail.