20 1 March1,September17th IF300 contract 3400 points.

By September 20 10, 17, the IF300 index was 2900 points.

Futures profit and loss positions = 300 * (3400-2900) *100 =1500000.

Futures profit and loss position = (selling price-settlement price) * number of short contracts+(settlement price-purchase price) * number of long contracts.

Your formula should be wrong.