Billibob, you are correct in that the published definition of the duration of a sitting is 10 days. My post was based on the old paper exam system where all subjects were conducted between Monday and Thursday within a week. But for practical purposes the 10 day duration does not appear to be usable.
The CAA website defines a sitting as a period during which exams may be taken. It also lists all of these periods for the current year. Each period is 4 days long and consecutive periods are separated by more than 10 days. So while the legal definition of a sitting may be 10 days, people actually wishing to take the exams need to look a little closer.