The bonus is calculated from the pool's fee of your referral and depends on his hash rate:
1 TH/S and more contact our support team for the details
up to 1 TH/S up to 50% of pool's commission
up to 100 GH/S up to 30% of pool's commission
up to 10 GH/S up to 10% of pool's commission
less than 10 GH/S up to 7% of pool's commission