According to this question and this question, the visits/day metric on sites' Area 51 page is calculated as the median number of visits per day over the previous 14 days. At the moment, the Area 51 page for the Mathematica site is showing a figure of 718.
But on the main StackExchange site's listing of sites, it's 717. That's also the number showing in the little box on the front page of the site.
It's a trivial difference, but it got me wondering if there was some kind of rounding bug or inconsistent calculation methods going on. Are the calculations different?