Are you sure it's not iTunes Producer that's asking for such information?
This is the iBA forums...you may have better luck asking in one of the other forums here:
Be ready to describe how many epubs/books have you ever published that you'd consider representing a 'catalog' of your work?
Yes my friend, it says at the top (iTunes Connect)
and I quote:
About Your Books
Once your application is approved, there is no limit on the number of books you can distribute through the iBookstore.
What I did is I clicked on (Publish) from the iBooksAuthor and followed the steps on how to publish it.
I've never published a book before; using iBookstore or iBooksAuthor.