The Collected Stories of Katherine Anne Porter is a book by Katherine Anne Porter published by Harcourt in 1965, comprising nineteen "short stories and long stories", as Porter herself would say. It won the Pulitzer Prize for Fiction and the U.S. National Book Award for Fiction.
Katherine Anne Porter wrote fewer than nineteen stories in her lifetime
The book referenced contains nineteen stories so Katherine Anne Porter must have written at least nineteen stories. I think the system had difficulty because the statement uses hedging language