I am learning to trade option and have read some books on it. Last thursday (20070621) I saw the stock index futures contract in our region was closed at 21917. and the 22200 call June option (expiry 20070628) was closed at 122, the broker's software indicated that the delta for this call option is 0.37. Next day(20070622) when I look at the daily report , I found that the futures contract was closed at 22014 ,up 97 points. Since the delta was 0.37 one day ago, then by definition, isn't it right for me to expect the call option price to be up (22014-21917)*0.37=35.89 points ? But the 22200 call option was accutally close at 130 , only up 8 points. Have I missed something here? what the call option rose far less than 37% of the futures contract.?