One round is composed of the 30-40 deep breathes, the exhale and hold, and then the big deep breath in and hold.....THAT is one round. One complete exercise is three of these rounds although I like to do four or five in a row to get me to my happy place.
You can do it for an hour or more, over and over and over again. I like to do that once or twice a week if I have the time. It's amazing.