It's covered in the linked PDF.

OLD BEHAVIOR: Report the highest transient voltage in the whole CPU, no matter how isolated or brief. This, too, overstated the prevalence and significance of fleeting peaks, which artificially inflated voltage reports by as much as 800mV. •NEW BEHAVIOR: Report the average voltage requested of the regulators, which presents a “whole chip” view that factors in sleeping cores, idle cores, and active cores. This is the closest any software monitoring tool can come to portraying the true electrical conditions of the chip, and it’s the same model our own Precision Boost 2 algorithm uses to make electrical-related boost decisions.