You are the first in the exchanger so it seems very complicated. It is a warning message sent to them. If the address you withdraw is incorrect, they will sent it to the wrong address. If you want to transfer BTC, you have to input BTC address. BNB to BNB. You will never send BNB to BTC address. If you do this you will lose coins. The transaction fees of each network and each ex-changer are completely different. Consider for yourself how much you are withdrawing and how much you can handle.