Those settings mostly affect the @page calibre inserts in conversions.
(I'm not sure <0 is valid )
Learn to Edit the code. Why?
Because there are as many ways margins get set as there are MR members

Been doing this (fixing
my books) and some still take quite a bit of detective work.

The
Code Inspector (in the Editor) helps track down where in the
Inheritance
BTW What is your Output format (you did read the note at the bottom of that screen?)