QTR-Quadtone RIP

I must be missing something in conceptualizing Curve Creation and I can't seem to get my pointy little head around it.  

I'm making a curve with a single ink (MK or PK on R1800) for matte (MK) or glossy (PK) paper.  In all the tutorials and guides for creating a new curve for a new paper/ink combination, the user is told to set an initial Highlight and Shadow setting of 6 - 10 in the Gray Curve tab.  It seems to me that one should start with these values at 0 (or blank) because during the process of "linearization" any adjustment made to the ink density curve by these settings will be nullified when the linearization factors are introduced folowing densitometry/spectrophotmetry of the gray scale printout.  

I would think that the linearization should be carried out before tweaking the Highlight/Shadow values, or am I not understanding some fundamental process or concept that QTR uses in generating an ink density curve? 

Any clarification would be greatly appreciated.