The new figure is separate from the 40-million-person breach Target announced last month. Not everyone who was affected by the previously-reported breach may be affected by this new revelation, though there is likely to be overlap between the two groups.
The new numbers suggest that the hack affected nearly a third of the country. According to the U.S. Census Bureau, there are about 240 million adults in the United States. By that standard, the breach exposed the financial information of 29 percent of Americans.
Target's stock is down more than 1 percent at the time of writing.