Gateway 2000, one of the leading direct marketing operators, has admitted it expects earnings to fall short of analysts' expectations for the third quarter ending September 30. Ted Waitt , chairman and CEO of the company, said its internal forecasts were overly aggressive. "When you fall short of your internal forecast two things happen: costs go up as a percentage of sales, and margins go down. We expect our unit shipments in the third quarter will still be up approximately 30 per cent over last year, but clearly we were looking to do better than that," Waitt said. In its second quarter, ended June 30, 1997, Gateway 2000 posted revenues of $US1.39 billion and net income of $56.5 million - up 10 per cent from the same quarter a year earlier.