Model-to-model distance module questions

Operating system:
Slicer version:4.8.1
Expected behavior:
Actual behavior:
hello 3D slicer experts, I made two models and calculated the distance between them with the model to model distance module , then I ran it’s vtk output file in shapepopulationviewer module.it gives me a colour bar.
1)what is the scale of this colour bar?
2) how to calibrate the colour bar, so that the scale of this colour bar shows the actual distance between the points of two models?
thank you