On EA's Help part on there site about Battlefield 4, they have given info on the install details for Battlefield 4 on Xbox 360.
Battlefield 4 on Xbox 360 will come with two discs, one being multiplayer and the other one being single player.
No matter what disc you put in first, you will have to install 2 GB to you're hard drive.
But you can also install more for better performance from each dice
Multiplayer Disc, has an additional 6.6 GB of install content and
Single Player Disc, has an additional 5.8 GB of install content.