Update: Seems like it's been fixed.
In the stats sidebar:
In the Area51 Stats section:
Is this a bug, or are 'visitors/day' different from 'visits/day'?
As the same visitor can visit the site multiple times, sure those are different things. But how 0 visitors manage to visite 3,402 times a day, you'll have to ask a magician – unless that's supposed to mean "there was no visitor accessing this site 3,402 times a day – everybody who visited had different numbers". Then it makes sense again :)
So I'd say: It's OK the numbers are differing. But at the same time, "0 visitors" looks like a bug – as I visit the site daily, and I think I'm not a zero :)