It's an aggregation of many trades throughout the day, before the close. The buy/sell indication means zilch - it only refers to whether the trade is above or below the last execution price, or on the bid/ask. Try it sometime - buy shares on the bid and it will register as a sell. You have no idea when trades hit if they are buys or sells. Sell the ask and it shows as a buy. Only when the share price is moving steadily in one direction or another are the buy/sells obvious. The daily buy/sell totals are useless.
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