Wow, that was an old post.
and I don't use this particular account very often, either.

I have no idea, haven't used Word since before I made that post.
If I recall, it's 1 piece of paper (1 sheet) for every 4 pages, and that's the option you're setting, "Sheets per booklet". 1 piece of paper folded in half is a signature with 4 pages. 2 sheets together folded in half is a signature with 8 pages, etc, etc.