MINNEAPOLIS — While the impact from the massive data breach at Target Corp. has worsened and the company continues to struggle in Canada, the nation’s No. 2 discounter is preparing to test a new, small-format prototype.

While the impact from the massive data breach at Target Corp. has worsened and the company continues to struggle in Canada, the nation’s No. 2 discounter is preparing to test a new, small-format prototype.

The retailer told the New York Times that it will open a 20,000-square-foot store near the University of Minnesota in late July. The concept, called TargetExpress, closely resembles Walmart’s Express format as well as echoing its name.

The initial test location will offer a mix of grocery and general merchandise, including basic apparel, home decor and electronics, as well as a pharmacy.

On a less upbeat note, Target revealed that the customer data breach previously disclosed is more serious than original indications, and includes such personal information as the names, mailing addresses, phone numbers and e-mail addresses for as many as 70 million individuals. Originally it was thought the breach involved payment card data from approximately 40 million customers.

The company also has revised its financial forecast in light of the data breach and ongoing weakness in its Canadian operation. Target has lowered its fourth quarter adjusted earnings guidance to a range of $1.20 to $1.30 per share from a prior estimate of $1.50 to $1.60 per share. Comparable-store sales are expected to decline about 2.5%, compared with an earlier projection of flat comp-store results.