How Does He DO That?

Little Brother was sitting at the breakfast table finishing his bowl of cereal.

"What time is it, Mom?"

"Ten minutes to seven."

He looked over at the digital clock on the stove and said, "No it isn't! It's nine! It's six-five-one!"

I am tutoring two high-school students who haven't grasped that concept. And I have no idea how he knows how to do that.