There is a story that a grocer's son was doing business, and when he was given a five-rupees' note, so he was giving four rupees. So the customer said, "Why you are giving me four rupees?" "No, I do not know what is the exchange." "No, it is six rupees." So "No, father will be angry." [laughter] Means he knows perfectly well what is five rupees, but he is innocent when he was giving four rupees.