Despite strong third quarter sales and earnings results, Dollar General CEO Rick Dreiling is cautious about the fourth quarter. He says customer spending has been erratic, which indicates uncertainty about the economy.

“It is my belief that our core customers are concerned about their financial outlook, which is resulting in a dynamic that is driving the current competitive environment to be more promotional,” said Dreiling.

For the fourth quarter, Dollar General is forecasting modest comparable sales gains, and flat-to-slightly decreased gross profits.

The company has 10,300 stores and plans to add 635 more during fiscal 2013, including 40 Dollar General Plus stores and 20 fresh-grocery Dollar General Market stores.