If you turn on the data cursor in the figure and then click on a point, these values are shown for that point.
If you want to reproduce the calculations, here's one way to do it. This "pop" variable is already sorted; you would need to sort your data to reproduce this.
load census
normplot(pop)
n = length(pop);
p = ((1:n)'-.5)/n;
popn = mean(pop) + std(pop) * norminv(p);
dataset(p,pop,popn)
