He says that he is cunning and that he acts wisely, as well as saying that he knows what he is doing. These are characteristics that he claims that crazy people don't have.
Explanation:
The narrator of "The Tell Tale Heart" exhibits strange, uncomfortable and crazy behavior in his murder plans and even the reasons for the murder make the reader see him as crazy. However, this is not what the narrator wants. He wants everything he says to be taken seriously by the reader and for this reason, he says that he has characteristics that crazy people cannot be astute, act wisely and know what he is doing.
