Time Left in Chapter (what constitutes a chapter)

I was hoping someone would know the answer to this, but I typically use <h2> as my chapter headings and at some points in various books use <h3> or <h4> as sub-headings. However this messes up the estimated time remaining in chapter. If I have many <h4> throughout the chapter, it can even say "chapter complete" on every single page turn.

So what constitutes a "chapter"? The paragraphs in between any two headings, no matter the type? Should I then change all my <h4> into paragraphs?