In 2012, how did the Republicans lose the popular vote for the House of Reps, but end up with the majority of seats?

In 2012, how did the Republicans lose the popular vote for the House of Reps, but end up with the majority of seats?

"Taking on injustices, 90 seconds at a time! The Civil Liberties Minute™ podcasts--with attorney Bill Newman, director of the ACLU's western Massachusetts office--highlight threats to our civil liberties and what you can do to protect our freedoms."