Fifteen Asia-Pacific countries signed the RCEP on Nov 15 after eight years of negotiations, in a regional trading agreement that covers a market of 2.2 billion people and a combined GDP of $26.2 trillion－both figures being about 30 percent of the global totals。请问这里的in a regional trading agreement是一个什么结构？为什么我总觉得它和整个句子的结构不搭咧！