Some after market action is simply a broker balancing his books or correcting errors in the day's trading activities. They may or may not be real trades, or they are reporting of trades that did occur during trading but were not reported or recorded correctly. It's often easier and cheaper for the broker to report an A/H trade that corrects an error then it is to correct it any other way. Mostly they are meaningless to the overall scheme of things, but I can recall in the past putting in a silly ask price as a GTC A/H order and occasionally getting a fill way above the close, usually for some odd number of shares.