See here: https://stackoverflow.com/tags/asp.net-vnext/topusers (though it doesn't always happen)
I've recently been retagging some questions and thus removing questions from a given tag. As such, quite often there end up being no questions within the last 7 or last 30 days. It sometimes shows this erroneous result:
0 Last 7 Days Infinity% unanswered0 Last 30 Days Infinity% unanswered 142 All Time 19.7% unanswered 
But if I wait a while (presumably due to some caching), it gets fixed to correctly say:
0 Last 7 Days 0% unanswered0 Last 30 Days 0% unanswered 142 All Time 19.7% unanswered 
