Resetting chapter numbers in an ebook with parts?

I’m compiling my first three novels into a single ebook. My problem is that I want to reset the chapter numbers at the beginning of each of the novels and can’t figure out how to do it. I found the Placeholder Tag <$rst> but the description doesn’t make much sense to me. Could someone tell me how to do this without having to edit the output file and change every title manually?

Thanks!

Henry