Muddiest Point for Week 4

I am still unclear on the post structure. From what I heard last week when a student in class asked this question to one of Dr. He's PhD students, I understand that we have to comment on the readings before the lectures. I know the readings should be done before the lectures on Tuesdays, but these blog posts have to be in by each Saturday before each lecture. So should I be commenting on the readings assigned for the week of 9/28 or 9/21?