@fairchild - welcome to MobileRead.
Your query isn't really related to this plugin at all, because the actual generation of the apnx file (which is what you want to change) is not the job of this plugin. All this plugin does is fill in a custom column with a total page count, which the calibre built in APNX generation code can optionally use to then create the APNX file evenly dividing the book by that total number.
What you are requesting is completely different - instead you want the html parsed to identify the page number at that point and for that to be used in the apnx file, if I understand it all correctly.
This is outside the scope of this plugin. Your only options would be to (a) make your own hacked version of the standalone APNX plugin (which user_none no longer maintains in its current state), or to change the calibre source code to use the alternate approach.
I have no interest personally in taking on either of those things since the current way of "estimating" a page count and generating an APNX based on that is perfectly adequate for my personal needs, so good luck with it if you decide to pursue it in one way or another...