On my post count graph in the profile it lists all the weeks and then it puts an entry for Jan 3rd at the very end. See screenshot below from when I mouse over it. I'm not sure where this is coming from as it doesn't represent any kind of maximum post count or anything. Jan 3rd also doesn't match up to the date corresponding to the week in January that actually shows up on the graph.
Anyway, it hasn't been a bother at all, just a curiosity. I figured I would post it up in case it was a symptom of a bigger problem.