the proportion who have at least a high school degree: estimate 65% vs. true 89%
the proportion who have an advanced degree: estimate 37% vs. true 12%
So basically what they guess is ±⅓ has no high school diploma and another ±⅓ has an advanced degree, while in reality ±^1^/~10~ doesn't have a high school diploma and ±^1^/~10~ has an advanced degree.
Meaning while in reality 77% does have a high school degree but not an advanced degree, the estimate is that only 28% does.