Pro Pride 1400 hitch - need help

A short update as promised. In July 5th forwarded trailer to the dealership for service according to the many other issues. This is my 3rd new trailer for last 20 years, so poor quality and culture of production during first year are not surprise for anyone. They will keep my trailer at least until end of August… therefore at this point cannot do anything with PP hitch, but decided to check up the correctness of the hitch bar assembly. According to the PP “Installation and Operation Instruction” (page 6) the dealer has set-up my “Hitch Bar receiver end” with Slide Pates DOWN and I’m asking your help and assistance to properly understand p. “C” and p. “D” page 6 of the Installation instruction. I’ve attached a few photos below with the measure numbers of my TV and TT, but CANNOT understand the difference between the “C” and “D”, because both points are expressing the same sense, as far I understood. So finally, how should I set-up my “Hitch bar receiver end” with the slide plates UP or DOWN? Could you send to me your professional advice please? I asked Sean, but he said:” The plates up or down only determine the offset you need to get the trailer to tow level.”
Thank you in advance for your time, support and attention.