I guess it's an all-or-nothing per day type of thing. Rather than a rolling count of how many views/impressions you get over time, it seems to reset each day. I... think?
My story, currently featured on the front page, got 200 views on May 1, 350 May 2, and 200 so far on May 3. The ad revenue page shows I got 1 cent on May 1st and May 3rd, but not May 2nd, so I'm a little bit confused there. Ad impressions are tragically only 221 for the past month (which implies 1 cent per 100 impressions), so it's significantly lower than the overall views.
Before that, I got ad revenue on November 2 (my birthday!), then a few days at the end of July, the first time it was featured on the front page. All still 1 cent. I don't care, really, but I am curious about exactly how this stuff is calculated.