This only occurs to computer science students as an initiative to make computer science more competitive in future.
Facebook is reported to adopt a new method on indexing all user's messages. Now, the first message is indexed as '0', no longer '1' as what we've been using before. This is because such method has been used by almost all programming languages in indexing entities like array. Facebook hopes that this change will motivate all computer science programmers in every universities to study harder, especially when they spend too much time on Facebook. Technically what would happen is, when a user who is also a computer science student sees such notification, he or she would immediately be reminded to programming language, and eventually this leads to homework completion.