Fixed Deposit

Respected Sir / Madam, I had made a fixed deposit on 13-10-2009 with PNB, amounting Rs 40,000 /- for 1 year having date of maturity 13-10-2010, the Maturity value rs 42,664 and interest rate is 6.5 % p.a , As we normally calculate the interest on rs 40000 @ 6.5 % for 1 yr the interest amount came to rs 2600 , but in confirmation deposit issued by bank the maturity value written as rs 42664 instead of rs 42600 ,what is the reason for this difference ?? And please also tell me whether bank consider the day on which we made FD with it for interest purpose ???