Do you have a v6 already and multiroom? Keep v6 as your main box and update (Home and then select update 360 from bottom of menu list). The box you are sent is likely a mini 360 without hardrive. One remote for updated v6 and one for mini. Make sure you update main v6 first if multiroom is your set up.
Just received mine and only found out by reading posts on her.
The mini box is about half height of your v6. You upgrade v6 first then replace your tivo with the mini box. Quite a few posts here now with same questions because we didn't get installation instructions.