Bullet stopping power chart? What are they going on?

Well right know in comparing 2 guns a Taurus 445 .44 special and a Taurus 617 357 magnum because I'm looking to buy one of them soon. So looking at the stopping power chart the .357 magnum is at the top the very best power along side .45 acp. So what are they going by on this chart?

Actual real knock down power or the number of people shot. Because if they go by a percentage of the number of people shot obviously the more popular round that more people use is going to win! I guess in my mind looking at the 2 rounds its hard for me to believe that 357 mag rated at 96% stopping power is that much more better then 44 special rated at 76% stopping power when the .44 is a bigger diameter bullet. Yes i know the 357 has more velocity but the 45 acp doesn't and thats rated at 96% also!!!

So what are they going by here??