Shares of Red Hat Inc., the largest seller of Linux operating-system software, fell as much as 9.3 percent Monday after the company reported second-quarter billings that missed analysts’ estimates.

Billings, a predictor of future revenue, rose 8 percent from a year earlier to $376 million, the Raleigh, North Carolina-based company said Monday in a statement. Analysts at CLSA had projected an increase of 17 percent, and Stifel Nicolaus & Co. predicted 14 percent growth.

Red Hat’s business is probably being hurt by a slowdown in Europe, while billings were also lower than expected because customers set up contracts with longer payment terms, said Abhey Lamba, an analyst at Mizuho Securities USA Inc., in a note to clients. Investors focused on the billings number even as revenue and earnings per share topped estimates.

“While Red Hat beat on revenues, EPS and cash flows, it missed the key billings metric by a wide margin,” Lamba wrote. On average, analysts had expected billings of $398 million, he said.

Red Hat shares dropped as low as $48 in extended trading, after falling less than 1 percent to $52.93 at the close in New York. Prior to the report, the stock was little changed for the year, while the Standard & Poor’s 500 Index had jumped 19 percent.

Sales in the period ended Aug. 31 rose 16 percent to $374.4 million, compared with the $372.1 million average analyst estimate, according to data compiled by Bloomberg. Profit, excluding some costs, was 35 cents a share, topping the 33-cent average estimate. Net income rose 17 percent to $40.8 million, or 21 cents a share, from $35 million, or 18 cents, a year ago.

Red Hat forecast third-quarter sales of $381 million to $384 million, lagging the $391.5 million average analyst estimate.