does this site "really" have 10000000 players?
The number on the front page is the number of accounts. I assume that is unclosed accounts. That would include people with multiple accounts that haven't been caught yet and a number of accounts that haven't logged in for a while.
The better metric would be the online now one but it would need to be sampled probably hourly over a few weeks to get any meaningful numbers.
I'm sure the site could create, or already has a query that would return a count of all members active over the past month that may even be more meaningful.