Do you calculate the interest for the day you make payment to a loan? (S=P(1+i)^n)

My question's below, I'm wondering n=1 or n=2?

Q:

Banks routinely borrow money among themselves overnight, in order to cover their transactions during the day. The interest rate paid on these one-day loans is called the overnight rate and therefore is a nominal rate of interest compounded daily, .

1.If ABC borrowed $25 000 000 and paid back $25 002 568 the next day, what effective rate of interest, , was it charged?