Do I make myself clear?
A statement said, usually sternly, to make sure that the listener understands the message. You cannot borrow the car without my permission, or you'll be grounded for a month. Do I make myself clear?
Do I make myself (perfectly) clear?
Do you understand exactly what I mean? (Very stern.) Mother: You're going to sit right here and finish that homework. Do I make myself perfectly clear? Child: Yes, ma 'am. Sue: No, the answer is no! Do I make myself clear?