Shares of Red Hat Inc., the largest seller of the open-source Linux operating system, fell in extended trading Wednesday after the company reported first quarter billings that may have missed some analysts’ estimates.

The shares of Raleigh, North Carolina-based Red Hat declined as much as 12 percent to $49.48, after earlier decreasing less than 1 percent to $56.50 at the close in New York.

Billings, a predictor of revenue, were $310 million in the first quarter, less than the $319 million estimate, said Abhey Lamba, an analyst at Mizuho Securities USA Inc., who rates the shares “buy.”