Different Strokes

So Dave decided that it's time for Cameron to learn his numbers. He grabbed some of Jackie's flashcards.

Dave (holding up #4): Cameron, what # is this?

CamO: 7.

Dave (holding up #3):What # is this?

CamO: S

Dave: That's not even a number!

...But, MAN, this boy can ride a 2-wheeler like nobody's business!