Applying substracting

I bought uyay this cars chocolate, he loves to eat them. It comes in chocolate covers with wrapping shapes as cars with multie color. During snack time like this i'll find some opportunity to teach him math. First we arrange the chocolate by colors and counting them. Then when he starts eating them i'll make him count the no of the chocolate before and after he takes one. Teaching him substracting concept. Therefor the more he pops into his mouth the more he counts. That way ummi dont feel so bad on the number of chocolate he ate today!!, bad ummi!!!!! Hahahhaha