If sending USD, you should use the Bank Account Number provided in the deposit notification; this is a virtual account number (VAN) that reflects a combination of both our bank account number (the first part of the Bank Account Number, before and not including the letter) and your account number at Interactive Brokers (the second part of the Bank Account Number, after and including the letter).
However, if the platform of your bank requires that you send the funds indicating the account numbers separately, send the funds to our bank account number and "for further benefit" to your account number at Interactive Brokers.