I'm not sure if this is a bug but I'd say it's been implemented wrong. For the statistics, most of them are cumulative and can be treated as such (i.e. the monthly statistics can just be the total of the daily statistics within that month). With "active users" that's not the right thing to do. If I have around 2 thousand users active each day, when I change to monthly statistics, I'd expect that to tell me how many users were active in that month but instead it just (seems to, I haven't dug into any code) total the daily statistics and gives me something like 60,000 "active" users, despite us only having 25K users in total.