I see you apply an age advice for certain collections. Where is this advice based on?
This advice is based on the advice of Common Sense Media, a US based non-profit organization. They are doing a terrific job in reviewing and rating tv-shows, movies, games and much more. Here's a quote what they say about themselves:
Common Sense is the leading independent nonprofit organization dedicated to helping kids thrive in a world of media and technology. We empower parents, teachers, and policymakers by providing unbiased information, trusted advice, and innovative tools to help them harness the power of media and technology as a positive force in all kids’ lives.
If you like to read more about how Common Sense Media rates, check this link