The "additional music composed by..." note at the bottom helps clarify the 4 songs vs. 5 issue. The 4 songs with names are likely the ones that are based on existing Linkin Park demos (we already know for a fact that 3 of those 4 titles come from demos as far back as Minutes to Midnight). Alex Puro may have assisted with the versions that ended up in the movie, but they pre-date his involvement so they'd technically be "Linkin Park featuring Alex Puro" songs (for simplicity's sake, Rob and Brad may have just left their names off of the credits for them, or they legitimately may not have been involved in the original demos for those tracks either). What we likely have with the 5 tracks heard in the videos is the 4 titled songs, plus one of the "additional" score tracks the band did with Alec later on. I have a feeling the opening song is the new one, as those lyrics were seen in the trailer for The Hunting Party, meaning they were written recently. So we know the "trailer feature" song is Luna, and the opening song is likely not one of the four listed in the credits. As for the other 3, your guess is as good as mine.