What question are we on?

So, today we did a little history test. Two, actually. Every week we do a post test about what we learned the week before, and a pre test about what we will learn the following week.
After every. Single. Question. Mom would ask what question we were on, to make sure no one(Charter) was writing their answer beside the right number.
After we finished question 10, mom asks, "What question are we on now?" Everyone raises their hand to answer.
Gage, sitting in his high chair, looks around and notices that our hands are up, and his isn't, so he puts his up.
Mom, jokingly asks Gage, "What question are we on, Gage?" Gage, without hesitating answers, "leven" And smiles sweetly.
We all check our books and look at him. He was right. How on earth did he do that?! Either it was just fluke, or he is the smartest one year old I know to remember that the last time we got asked the answer was 10!