"About 5.3 million taxpayers claimed approximately $19.2 billion in [premium tax credit (PTC)], reporting an average credit of $3,620.... Approximately 3.3 million taxpayers reported excess [advance premium tax credit (APTC)] (meaning APTC paid during the year exceeded PTC). The average amount reported as excess to be repaid was about $870, for a total of $2.9 billion.... The statutory repayment caps affected approximately 921,000 taxpayers or about 28 percent of those who reported excess APTC.... [A]pproximately $874 million in excess APTC for tax year 2015 was above the statutory caps."