Help Understanding Scalar Value Units

Hi all! I am pretty new to 3Dslicer and was wondering if anyone knew if the scalar values had any specific units or if they are just relative (the thicker the area the higher the value)? I am working on CT scanning shells to look at how thickness is allocated throughout the shell for a research project and I haven’t been able to find anything to help me figure this out.

I made my thickness heatmap following another post on here (stl model > segmentation > label map volume > Simple Filters > Binary Thinning Image Filter > Danielson Distance Map Image > Probe Volume with Model)

Any help would be much appreciated!