If I'm not mistaken - and @piedpiper can probably correct me on this if I'm wrong - that was simply the first payout date. Since then, the payouts have been daily, depending on when your post is created. At first since 7/4/2016, they were 24 hours after your post. Now they're 12 hours. After that, any earnings you generate on any given post are paid out 4 weeks later. That's per post.