How do matomo calculate the unique pageviews in VisitsSummary module,Why the percentage of unique pageviews in pageviews is significantly reduced In matomo 3.2.0

How do matomo calculate the unique pageviews in VisitsSummary module?
Why the percentage of unique pageviews in pageviews is significantly reduced In matomo 3.2.0

eg:
I found In the same number of pageviews
the percentage of unique pageviews in pageviews is 83% in matomo 2.1.6
the percentage of unique pageviews in pageviews is 28% in matomo 3.2.0