Curren population is 347.533.640

99.9 => 347.533 people

99 - 99.9 => 3.127.802 people

99 - 90 => 31.625.562 people

99 - 50 => 142.141.258 people

50 - 0 => 173.766.820 people

Multiply the population by the percentage? (I didn't find anything on that page suggesting that it wouldn't be the case.)

342 million * 0.5 = 171 million people who are in the bottom yellow line. The top darker green line is 342 million * 0.001 = 342 thousand people

I think you can do the others yourself if you like.

Around 350M Americans, so the bottom 50% is about 175M, next 49%'s about the same, top 1% is 3.5M, top 0.1% is 350K people.