What do the numbers in red that are listed in the songs represent? I play the mandolin and I am interested in the lyrics and the chords to each song. Thank you!
Those are the chords, in the 1-4-5 notation, aka the Nashville Number System. This allows you to easily figure out what the chords are in any key you might want to play the song in.
Here's a video that explains how the system works: http://toneway.com/learn/get-started/lesson-three/chapter-4