What do the percentages mean in the audio quality stats section?

Call values for each of the metrics (jitter, racket loss, round trip time) vary with each voice data packet transmitted; these are represented as percentiles. A 30% value of jitter 45 ms means out of all jitter values that occurred during the course of a call (with each voice data packet), 30% of the values are less than or equal to 45 ms. That means 30% of your call had jitter less than or equal to 45 ms.