Square Enix has shared a few more details on Crisis Core: Final Fantasy VII Reunion, including the fact that the game includes 300 missions for you to tackle.
Crisis Core: FFVII Reunion packs in 300 SOLDIER Missions for Zack to take on. Completing these will get you Materia, and will also increase how many accessories you can equip. Each mission has its own difficult, and the challenge will get more intense the deeper into the game you go.
We know that some of these missions are going to have multiple components as well. For example, M1-3 are missions from the weapons development team, and M1-3-2 involves testing out new weapons made to counter Shinra weapons.