So you say, this is the counting system for the last 30 days? It is the up and down votes for the posts not older than 30 days?
In that case, it's a feature.
Yeah, I think it had been noted that Eliezer kept getting "top contributor, past 30 days", even in months where he wasn't present in LessWrong at all -- just because people were upvoting past posts he made.
It was so decided that "past 30 days" should be counting votes on posts/comments made in the last 30 days, as better indicative of this month's contributions. Feature, not bug.
At the moment my karma is 450 and -50 for the last 30 days. I had never 500. Also not a month ago.
Must be a bug in the karma counting system.