From Halopedia, the Halo wiki
The video takes the form of File:CHELAN_20200420, a file part of Director Schaefer's "content series" in ONI Section 2's public awareness campaign regarding the UNSC's role in colonial security. The series is aimed at educating UEG citizens on the history, evolution, and application of the Spartan Program.
ONI Screen activates, showing the file name "File:CHELAN_20200420, and a wave form of a "Comms Officer". With the words "Transmission suspended" in the center of the screen.
ONI Screen deactivates, and the Halo 2 Anniversary logo appears saying "Available now" below it.
The filename of "CHELAN 20200420", unlike those for the videos released for the launch Halo: Reach and Halo: Combat Evolved Anniversary on PC, does not correspond to the release date of Halo 2: Anniversary. The CHELAN part of the name refers to the Chelan app that requests permission when the player logs into Xbox Live through Steam. The number below LINK "20040911" is a reference to the original Halo 2 release date on November 09, 2004.