In the WiiWare version, the player purchases the core game, or "Main Story", which includes the Prologue, Ceodore's Tale, and Kain's Tale, while the additional supplemental installments are released as add-ons. The first, Rydia's Tale, was released along with the "Main Story." There are 11 chapters in total. The first four are included in the "Main Story."
Source: Wikipedia, "Final Fantasy IV: The After Years," available under the CC-BY-SA License.