T-Trades are from somebody hiring a market monkey. Say you want to sell 20M shares of DEAC. You hire a MM, and they proceed to dump it throughout the day. Then after hours you'll see a T trade for the total amount.. (19,244,877 in this case)....Also sometimes you'll see 'Avg' trades during the day....
And T-Trades before the market opens are also market monkeys.......z