exporting XYZ points from mesh; no nominal CAD

[[Ch...]]

First off, I'm a newb on my GOM and Zeiss inspect(I'm actually using ATOS Pro v8).  

I'm looking for best practices for exporting XYZ points when you section a mesh.  I was successful in exporting my points but I want to feel out what other people are doing.   

Here is my current workflow:

1. scanned the part

2. created a fitting plane to use as my reference plane

3. Used "construct single section" to create my line profile

4. Then I just used Export>ASCII file

 

This worked but I noticed something weird.  I sectioned my surface 4mm above the reference plane.  But my Z value on the ASCII is at -3.27mm.  The XY plot for the blade I exported looks right, so I know it exported the section I wanted.  But I can't figure out why my ASCII Z values aren't closer to 4mm.   To complicate it, I created a local alignment on top of the blade, I think my ASCII file might be aligned to that, but I'm not sure.  

To summarize:

An I using the best workflow to export XYZ points from a mesh with no nominal CAD?

How do I know which alignment my ASCII file is using?