I have attempted doing some research into those purple stickers; however, I was unable to come-up with any explanation as to why these sheets have those stickers and what they mean (if anything). I have some close-up images of the stickers and a few additional pictures of those Neo Discovery Sheets here:
www.elitefourum.com/t/amazing-un-cut-sheet-find-need-some-information-help/16705/1