Sleep Number shares were off sharply in Thursday's trading, a day after reporting quarterly revenue that was slightly below Wall Street expectations.

"We feel great about the company and where we are at," said Chief Financial Officer David Callen. "What the stock market does or doesn't do, we don't have control over that, and we can't spend a lot of time worrying about that."

The Minneapolis-based maker of beds and other sleep products earned 80 cents per share in its first quarter, a 54% increase over the same period last year. Analysts were expecting 73 cents a share. Revenue was $426.5 million, up 9.7%, but slightly below expectations.

Same-store sales growth was 5%, as were new-store sales. Sleep Number opened 15 new stores in the first quarter and 20 stores in the fourth quarter and some of those were store relocations within local market areas.

Some analysts digging deeper into the first-quarter results saw some concerns. "Sleep Number is struggling to drive comparable mattress unit comps," Seth Basham, an analyst with Wedbush Securities, wrote in a research note to investors. "This remains our primary concern for Sleep Number."

Basham said the consensus estimate for comparable sales was 6.3%.

The quarterly results were announced after the market closed Wednesday. On Thursday, the company's shares lost 18.5% of their value, closing at $39.16. Shares are still up 23% year-to-date, and that still makes Sleep Number among the better-performing stocks of Minnesota companies.

Sleep Number reiterated its guidance for 2019 full-year earnings. The company still expects between $2.25 and $2.75 earnings per share for the year.