I am not an expert either, but my guess is that Dec contract is probably not as liquid as the Sep contract during the after hours trade and/or the time of last trade for each of the contracts could be off by that much to show that kind of difference.
jd, I'm not sure what that means. I think Steve Lee on Zeev's old thread would know. Susan G would also. Often times in drops the futures trade at a discount to fair value.
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