Twitter is growing, but it’s not just the monthly active users that matter.On the company’s Tuesday earnings call, CEO Dick Costolo said that the size of Twitter’s audience is two to three times as big as the number of monthly active users—271 million—on Twitter. That means millions of users who aren’t on Twitter are seeing tweets, including those embedded in the media, or shared by friends.“We will position ourselves to reach the largest audience in the world, and everyone on the planet,” Costolo said on the earnings call.