Okay, so I am correct in leaving that setting
unchecked then.
So now how do I tell calibre not to build an additional table of contents since the file already includes an embedded one. I'd rather not remove the XPath expression because I
do want it to make the page breaks at the specified areas. (I actually tweaked that a little bit to include h3 headings, plus the words, prologue, preface, and introduction.) And if I remove that line then it won't page break at those places.
ETA - Oh nevermind, I think I may have found it. Under
Number of links to add to Table of Contents, it says if I set that to 0, it'll disable it. So I'm going to try to build that way now.