Hi William,
As a beginner I encourage you to first practice sets of 10 of each movement. Then later we’ll progress to doing 20 of each movement, which is the ideal number for a set. By the end of this course we’ll be guiding you through a set of 20 of all seven movements.
Why is 20 the ideal number for a set? My understanding as I learned from Bruce is that the ideal of 20 was derived over hundreds of years of research by the masters of Dragon and Tiger. After observing thousands and thousands of practitioners they concluded that for most people 20 repetitions gives the best value in terms of developing more energy and flexibility. They found that when someone wants to practice more than a single set of 20, the best strategy is to do multiple sets of 20.
By the way, you could also do a set of 6 or 14 or 18 or whatever even number you choose that is 20 or less.
So if you wanted to practice one set of 20 and another of 10, that would be fine.
I hope this helps,
Bill