I Draw Number Oh!

On Sunday I think it was, Matthew was having some fun colouring with his markers, and started drawing what looked like upside-down "U" shapes.  He seemed to take a little more time when doing it than his normal scribbling, the kind of time he takes when he's trying to draw sharp corners to make what he thinks is a Triangle.  After a few of them, and a couple with closed bottoms so they looked almost like "0" shapes, he started getting excited and telling us "I draw number O!"  I tried correcting him that it was a zero, not an "O", but then I realized that he just had the definition of number wrong, and that he was indeed making "O"s, as in the letter, just calling it a number.  He is so smart sometimes!