Let us say you have lent 10,000 XRP for 7 days at an interest rate of 0.06%.

0.06% of 10,000 XRP would be 6 XRP. And because you have lent for 7 days, interest generated per day would be 6 XRP. So your total interest for 7 days is 6 x 7 = 42 XRP. Bitbns charges a 15% fee on the total profit. 15% of 42 XRP equals 6.3 XRP. 

Net profit 42.00 - 6.30 = 35.70.

Hence, your net profit on lending 10,000 XRP for 7 days at 0.06% interest rate is 35.70 XRP.