read the article again:
to answer your first question: "Remember, when you see those A1, A2 thingies, that means to do one set of A1, rest, then one set of A2. Superset like this until all "A" sets are completed, then go to the "B" exercises and so forth."
This applies to day 6 in the manner do all sets of A then move on to B
To answer your second question:
"Day 6 (Explosive Strength)
Rest: 60 seconds between consecutive sets
Tempo: As fast as humanly possible while maintaining proper form."
use whatever weight fits these parameters