Apparently, Halo 5: Guardians is so vast you don't get everything on Blu-ray package, and a part of the game-multiplayer-maps will be downloaded separately with an update that will start when you first start the game.

Microsoft explained in Game Informer, specifying that while the digital edition of the game will come in a single download from 55 GB without additional update, anyone who buys the game disk will have to download an update around 9 GB that will contain the multiplayer maps.

If you take the game retail edition tente then the download time of this additional data, but if you have booked in digital preload is available already from this morning and you should then get to day one without additional expectations.