To get the Daily Interest calculated based on the Annual Interest 4.39% (Bonus of 7.5% already included) then I result in 0,0121944444 and not 0.01178082%.
My calculation is 4.39/360=0,0121944444 to get the daily interest. But on my EARN BTC tab is just @ 0.01178082% * per day given..
You have to divide it by 365 to calculate the daily APY rate. Still, there is something strange on the Freebitco daily APY rate. The daily APY rate is 0.0109589% for those user who doesn't have premium membership benefits.

It becomes 365 × 0.0109589 ~ 4% for a year. Which is almost 2% less than it should be. By considering your interest rate: 365 × 0.01178082 ~ 4.3%, it is also 2% less than it should be. I can't recall whether TheQuin had clarified about the interest rate or not here in the forum. My calculation doesn't match with the exact rate, but it is pretty close.
@hosseinimr93, you are too good in this kind of calculation. Do you have any idea about this wrong calculation system of Freebitco interest rate?