You don't have enough memory in the memory card
A casual, subtle way of calling someone stupid, as they do not have enough memory in their memory card. Or, in other words, not enough memory in their brain.
Person 1: Does 2 + 2 = 5?
Person 2: You don't have enough memory in the memory card. Is your memory card set correctly?
Person 2: You don't have enough memory in the memory card. Is your memory card set correctly?