Since every woman's breast and chest anatomy are different (different chest width, different chest height, different chest shape, etc.) and since implants come in a variety of shapes and sizes, there is not a specific volume of expansion for a "C cup" breast. Since you are undergoing tissue expansion, you will be able to work with your plastic surgeon to determine what volume of breast size fells and looks best for you. When you get to a point in the expansion process that you are satisfied, let your surgeon know. They will then, most likely, "overexpand your tissue expander and then plan on exchanging it for an implant in the range of volume that satisfied you.