I have a question about margin calculations.

If I buy an at-the-money NIFTY put and a NIFTY future, both with same expiry, say April 2014. I then sell an ATM NIFTY call with same expiry. I am essentially trying to setup a put-call-futures parity condition, which is a hedged position. I expect the margin for such a position to be significantly low, but when I calculate the same using the SPAN calculator, I get the total margin for this position as Rs. 31,592 (for strike price of 6700). Can anyone please explain why the margin should be so high even for such a hedged position?

Thanks in advance.

-Shivam