The settlement price of Shanghai and Shenzhen 300 index futures contracts is the delivery benchmark price. The settlement price of the Shanghai and Shenzhen 300 index futures contract is the arithmetic average price of all transactions of the Shanghai and Shenzhen 300 spot index in the last two hours.

The IF 1005 contract of Shanghai and Shenzhen 300 stock index futures was delivered on may 20th, and the settlement price of the IF 1005 contract was 2749.46 points. Explain that 2749.46 is the arithmetic average of all transactions in the last two hours of the Shanghai and Shenzhen 300 spot index.