What does "not funded by you" mean in Vanguard's college savings planner?

One of the items on the left hand side is "% of cost you plan to cover" which you've set to 50%. So you're expecting that half the cost will be covered by someone else. That's the "Not funded by you" section of the results.

This "Not funded by you" number includes things like financial aid, scholarships, loans. Basically anything that is paying for college that isn't your savings.