Supporters of the ASEAN-China Free Trade Area (ACFTA) argue that numbers tell the story. And indeed, they do. But while those advocates focus on big numbers, such as the billions of consumers in the new market or its combined gross domestic product, the most important figures are much smaller. Forget the billions and trillions: the real significance of the FTA is in the simple “10 plus one” formula or, more accurately, one plus 10, given China’s predominant position. For in addition to moving the focus of regional decision making to the north, the new free trade area will change the way Southeast Asia integrates, fundamentally altering the region’s organizing principles. Unless ASEAN can effectively transform “10 plus one” into “one plus one,” through greater ASEAN coherence, it will be overwhelmed by China’s rise.