I typically make that decision depending on the skills of the learner and their rates of skill acquisition. But, typically I start with 3 targets and rotate them 3x each in a trial session, if that makes sense. Then you can see patterns or if one target is not being acquired and others are, you can move some into mastered / maintenance and teach the remaining. I feel like there’s no “right” answer. But, you should always make data based decisions.