If we consider company A (whose stock is listed under F&O) is releasing their results on Tuesday. Let us consider that a buyer expects the share price to increase to Rs. 100 from Rs. 90, and thereby purchases the futures contract on A at Rs. 90. When the company A declares the results on Tuesday, the stock having risen to Rs. 100, the buyer will make Rs. 10 per share. Typically he has not put the entire amount of the contract but a portion of it, ie. 12%-15% for trade. Let us consider 100 shares in lot A and buyer puts up 12% of 9000 ie. 1080. If the price increases by Rs. 10 per share he will make Rs. 1000 but if the price falls to Rs. 80, the buyer will make a considerable loss.