The "yadda yadda yadda" is a Seinfeld reference that just means "all the rest that I'm too lazy to say" - very funny -
here
It was meant to describe any of your following paragraphs after the first one in the chapter. It was my bad that I didn't notice it was the last line in the chapter.
It is very confusing that ALL of your paragraphs are assigned the class of "chapstart". It should only be applied to the starting paragraph of your chapter, all the rest would just be <p> with no class.
Cheers!