Common Data Set -GPA UNC

From what I read UNC’s calculated GPA is in line with public NC high schools’ systems. I think. But I am not sure. Starting this year public schools in NC are decreasing their GPA values (devaluing AP and Honors credit) to line up more with national norms.

Is the reported GPA in the Common Data set at UNC a reflection of the GPA system used by NC public schools last year? Or is it more in line with national norms?

For example in 2017 a student at a NC high school would have a 4.8. Recalculated to 2018-2019 it would be a 4.5.

When UNC says their average is 4.6, which scale are they using?