(Reuters) – TD Ameritrade has seen the number of investor orders for shares of Alibaba Group Holding hit 70 percent of the number of orders that came in during premarket trading at the Facebook initial public offering. The number of investor orders represents almost three times what the firm saw in premarket trading before the Twitter IPO, JJ Kinahan, chief market strategist at TD Ameritrade, told Reuters in an interview Friday morning. TD Ameritrade is not disclosing specific numbers. The brokerage has more than 6 million clients. Further company coverage: [BABA. …