I don't understand the point of the analysis. A slightly higher percentage of things might be posted at 8:00 on Wednesday. That doesn't mean it's the best time to post. In fact it might be the worst time to post because you are competing with all those other people.
Here's a better analysis for HN: https://silverman.svbtle.com/the-best-time-to-post-on-hacker...
It measures the liklihood of reaching the front page at a given time, not the number of posts at that time.