How can UNC-Chapel Hill have an average admit enrolled GPA of 4.7?

Here’s a question…are high school credits earned in middle school calculated into the GPAs (weighted/unweighted)? For some reason, in my Maryland county, Algebra taken in the 7th / 8th grade, and any FL taken starting in the 6th grade (all for HS credit) are never coded as honors so those classes bring down the weighted average.