It's a liability thing as a disclaimer that mistakes can happen during factory packaging and you MIGHT not get a full set. Most blind boxes should have something similar. I've seen every Square blind box include it and I still have gotten a full set on ones I've ordered. Odds are, you'll get a full set of 1 of each, but the possibility does exist to end up missing 1 and get 2 of another, so it's just a warning to avoid complaints or custom service issues.