Regardless of the grouping, we want to make sure to take enough rest between sets (a minute or so) so that we’re fully recovered, or at least mostly recovered. Trying to lift weights when you’re totally out of breath is a recipe for injury.
If you see a grouping consisting of two moves—say A1 and A2—calling for three sets of each, that means you do one set of A1, then rest a minute or so, then do one set of A2, then rest another minute or so and go back to the second set of A1. Then continue in that manner until you’ve done all three sets of the A exercises before moving on to the B pairing and doing the same thing.
More information onspecific training and programs can be found at BenBruno.com.