Since this fix, the questions/day statistic for all beta sites is being calculated with a different formula than before. The old method calculated the number of "questions per day on average over the past two weeks" as per the mouseover text. That's also the number reported in the site index.
The new version shows the average over the entire history of the site. For sites younger than 2 weeks old, this will be the same, but for older sites it could be quite different. To give an extreme example, Italian Language is reporting 1.2 Q/D, while by the old method it should have 0.1 Q/D. Most other low volume sites like Beer, eBooks, and Sustainable Living are also over-reporting based on their high initial volume from private beta. On the other hand, Code Review is only showing 12.3 Q/D even though they're over 30 recently.
This is a rather minor bug, in that the stats aren't something one should obsess over anyway (what matters isn't absolute values but relative growth), but they should at least be described correctly. If the old method is the desired one (which I suspect), it should be switched back. If the new method is better, the mouseover text should be edited to remove "over the past two weeks".