What option should I click when replying to consulate when called in for interview?

After I submitted my documents via dropbox, I received an email saying I need to come to the consulate for an interview. In that email I saw three options “Thanks, I will be there”, “I am confirming the appointment”, and something like “No …”. I clicked on “I am confirming the appointment” button. Is that the right one and what is the difference between that and “Thanks, I will be there”? Do I need to make my appointment or is it scheduled already?