The "Refer and Earn" formula is based on a 10% rakeback of the referred user. Here is a breakdown of the equation:
Your earnings are calculated from the house edge, which is the "profit" of a casino. Each game has an RTP (Return to Player), and the house edge is calculated as 1 - RTP. You will then earn a percentage of this house edge. For example, if a player plays on a 99% RTP game and your commission is 25%, you will make (0.25 * (1 - 0.99)) = 0.0025, which is 0.25%. Sportsbook bets do not have an RTP, so the assumed house edge is 1% (99% RTP).