Potbelly (NASDAQ:PBPB) reported fiscal 2013 fourth-quarter and full year earnings after the bell on Tuesday that proved a mixed bag for the sandwich chain. For the period ended Dec. 29, Potbelly posted a profit of $0.06 per share on net income of $1.9 million. That was two cents better than analyst estimates for earnings per share of $0.04 per share in the quarter. Unfortunately, revenue failed to impress. Quarterly revenue inched up 1.7% to $74.8 million, which was below estimates for $76 million in revenue.

This was Potbelly's second earnings report since going public in October. Shares of Potbelly popped more than 125% on the company's stock market debut; hitting $31 a share, up from the stock's initial offering price of $14 a share. However, Potbelly was trading lower after the market close today because of the fast-casual chain's latest earnings.

Potbelly opened nine company-operated stores and four franchised locations during the fourth quarter. However, same-store sales growth was done significantly. Comparable store sales increased just 0.7% in the period, which was a far cry from the company's 2.5% spike in comps that Potbelly reported in the third quarter. Potbelly's full-year comparable sales growth wasn't much better at 1.5%.

Despite a challenging fourth quarter, Potbelly's CEO Aylwin Lewis is optimistic about the company's future. "Our long-term growth plan remains very much on track to achieve at least 10% unit growth and 20% plus EPS growth on an annual basis," he said.

Shares of Potbelly were trading around $22.40 as of 4:35 p.m. on Tuesday.