Well, it is the 10 most active, so currently 13 rounds, however, this changes pretty much every week and will constantly go up. I may extend it to 20 or 30 most active. I set it to 10, as there aren't really that many people who are vocal about it as you can tell by some of the other prediction league threads.
However, if you are doing good but haven't been in 13 rounds yet, then you should be in the top 30 groups.