Thunder, I just added up the percentages from the chart that was included along with the graph. If it still doesn´t make sense to you please message me and I will give you a really boring explanation of how it works.
JohnSchwab909 is absolutely correct. The chart should read: You are bigger than or as big as this percentage of the population. If you want to know how many people you are bigger than then you will have to read the value of the line one over to the left of your length. So if you are 6.25” long, then you are bigger or equal to 61% of the population. But, you are only bigger than 52.2% of the population, because the other 8.8% that add up to the total 61% are the same size as you.
Sorry for the mix up. The numbers are still valid, but this does make a bit of a difference. Hope what I´m saying now is accurate.