When enough entrants qualify, at least the top 3 are paid in a weekly league and at least the top 5 in a monthly league. With more entrants, more ranks are paid. The standings then say that further ranks are paid too.
The higher the rank, the larger the share. Payout now next to each rank shows what that place would get if the round ended now. Monthly prizes can have a cap per player, and the page warns you when it applies.