In A Day No Pigs Would Die, how did Apron surprise everyone?

Apron surprised everyone by giving birth to twin calves.

“A matched pair, they be. Always wanted a yoke of matched Holstein oxen to take to Rutland. Now, thanks to your stout son, Haven, I got me the pair. Finest oxen in the county, they be. And come Fair time a year, they’ll do Learning proud.”

“Apron had two?” It was all I could say.