The earliest date owners can book is 11 months before checkin. And yes, CCV owners who want a studio in December usually have to book on the first day 11 months out, promptly at 8:00 AM Eastern time. Some do walk their reservations.
You can book up to 7 nights on the date that’s 11 months from check in. Walking means booking a reservation that begins sooner than your actual desired dates, then modifying it every few days until you reach the dates you want. For example, you want to stay December 8-15. On January 1, you book December 1-8. Then on January 6 you modify to December 6-13, and on January 8 you modify again to December 8-15.