They are using the 2024 1st quarter statistics. The author has linked to chart titled: The Most Famous Royalty (Q1 2024)

The results for fame are:

Harry, 100%
William, 97%
Andrew, 97%
Queen Elizabeth, 96%
Charles, 96%

But the page also shows popularity ratings and those are:

Harry, 34%
William, 67%
Andrew, 9%
Queen Elizabeth, 77%
Charles, 58%

So, although the chart is clearly labeled as showing that the rankings refer to Fame, the author is claiming that this chart shows that Harry is the most popular.