Binance’s margin account interest rate is calculated on an hourly basis, if it's less than 1 hours, it will calculate as 1 hour.
If the daily interest rate is 0.02%, the hourly interest rate is calculated as 0.02%/24
The calculation formula: I(Interest) = P(Borrowed Money)*R(Daily Interest0.02%/24)*T(In Hours)
If A borrowed 1000 USDT at 13:20, and repaid at 14:15. The interest rate is calculated as 1000*(0.02%/24)*2=0.01666667 USDT
We may adjust the rate of interest from time to time, you can find the latest rate of interest here: https://www.binance.com/en/margin-fee