There is a traditional version of the dance which uses at least two B parts - I think it then repeats two A parts and two B parts. However, in competition, it is usually done with two A parts - the "step" on the right foot followed by the "step" on the left foot - followed by one B part - the "set" on the right foot only.

Actually, I lied - before the dancer begins dancing, the musician(s) plays the A part through once, followed by what I said above. So, if you attended a competition, you would typically hear three A parts followed by one B part.

Don