Margin funding is calculated based on the amount, interest rate, and the length of time that funding was provided/taken.
Funding takers and providers will pay or receive funding interests in the same currency they borrowed.
Margin funding interest to pay:
Please note, if users reserve and return funds manually within an hour, regardless of whether the funding has been used in a financed position, they will pay a full hour's interest.
Margin funding interest earnings:
The provider of funding will receive the interest paid by the user borrowing, minus a 15% fee. Please note that a 18% fee, instead of 15%, is charged when funding is opened with a hidden offer.
For instance, if you have an active $10,000 USD offer at 0.06% you would earn $6.00 USD per day. On those $6.00 USD a 15% fee is charged, so $0.90 USD. You will receive $5.10 USD per day that the offer is taken.
Bitfinex will charge a minimum of one full hour's interest to the borrower on any funding that is borrowed and manually returned. A user that has provided the funding will receive the full hour earnings, minus a 15% fee.
If you have any questions contact the support team for further explanations, by providing as much information as you believe is relevant.