From the introduction:
Welcome to a special introductory edition of the Princes of the Apocalypse™ adventure, designed specifically for D&D Encounters™ (an official in-store play program) and the D&D Adventurers League™ (the official D&D organized play system).
This edition of the adventure is designed for 1st through 4th-level characters, and is divided up into two parts, each of which contains a number of adventure scenarios. Characters who finish both parts of the adventure should reach 5th level at the end. Characters of 5th level and above cannot play in this D&D Encounters edition of the adventure, though they can play the full adventure of Princes of the Apocalypse. Each part of the adventure should be played over multiple sessions of play. For D&D Encounters, the recommended session length is two hours. The full adventure contains additional play beyond this edition (see “Additional Play” at the end of the adventure).