I assume that CC = credit card. It is likely that interest is calculated on a day to day basis. It should (in theory) be easy to work out unless there has been a lot of movement with additional debits and credits. My guess is that the figure is based on the balance as at the last statement and goes up to the date of the latest one. If there has been no movement, the calculation is the balance * annual percentage rate / 365 * by the number of days between the 2 statement dates. It gets more complicated with debits and credits going through. If so, you will need to calculate each day individually and add the lot together. Excel is your friend for this.
Does this make sense?