Bob mane correct the black plastic is mud ring flush means the front of tile AKA finish wall.
none of those measurements matter with tape measure The valve is set according to where finished wall is and that's it . there is some play but all of us that have installed hundreds have had close calls or ripped out walls to fix screw ups , whether they were our fault or others we are the ones that fix it. your the plumber so you'll be the one that deals with it , if in doubt get the trim out and check it.