This is in fact confusing.
This part of the Vinaya is called the “Khandakas” which are traditionally grouped into two books or volumes: The Mahavagga (“great book” or “great volume”) and the Cullavagga (“small book” or “small volume”). Of the 22 Khandakas (you can say “chapters”), the first 10 form the Mahvagga and the remaining 12 the Cullavagga. That means on SC the Mahavagga is Kd 1–10 and the Cullavagga is Kd 11–22.