Mrs. weston asks colin if he wants his sandwich in one piece, or cut into two pieces. colin tells her to keep it in one piece because he isn't hungry enough to eat two pieces. in the context of piaget's theory, colin's answer suggests that he does not:

Colin's answer suggests that he does not yet understand conservation.
He cannot comprehend yet that if you cut one thing into two halves, it is still the same amount, just split in two. That's why he tells Mrs. Weston not to give him two pieces because he wouldn't be able to eat so much and he doesn't realize that those two pieces are the same as one large sandwich.