I can only definitively say that,
mordr_form_5_ranks_plus_one = 27
It only exists for ease of use for ranges. This engine uses non-inclusive upper bounds so if you want a value included in it, you need to add one to it, so last applicable value + 1.
My guess for the other is
mordr_form_0_rank = 21
Looking at a glance it seems to only use it as a way to numerate their rank's depth so I assume you want form/rank 1 to be 1, but I could be wrong. I've never used the pack before, and I don't know if there will be unintended consequences. The other reasonable answer would be 22, but I assume he would just subtract the first row in that case.