What has sales figures got to do with player count?
You can't buy DCS multiplayer on it's own, it comes packaged with SP. How does anybody know how many people play single player, you cant quantify that by sales.
I know 2 people who bought into DCS, never played MP but have now given up playing altogether, do they still count as SP's?
I know someone else that bought it purely for MP, and that means he also bought SP, does he count as a SP?