What is the correct interpretation of the following lines from act iv, scene ii, of twelfth night?

Maria and Feste conspire to present Feste as Sir Topaz, the curate, to Malvolio, who is hidden from view. Feste tries to convince Malvolio that he is crazy, and Malvolio continues to insist that he is not, that he has been wrongly incarcerated. Feste then confronts Malvolio as himself, and torments him some more; he fakes a conversation with himself as Feste and Sir Topaz, and Malvolio begs for paper and ink so that he can send a message to Olivia. Feste promises to fetch these things, and exits with a song.

Hope this helps. ;)