TM is the stateroom category and yes, it is a Terrazza Premium Vista. Looks like 410 sq ft total area (incl balcony) - huge. You could enter from Deck 5 port or starboard outside decks, through the Carnivale bar. The stairs near your cabin would be crew only (I think).
AS mentioned, the Bridge is on Deck 8, so had to go inside and up some stairs to continue.
I thought this was a nice touch. Even a caveman might figure out they are on deck 9 and not 6