How does matlab compute confidence interval for power function in cftool ?

Hi,

I am approximating the parameters of a power function (y=Ax^B) derived from sampled data using cftool. The result is good and I guess is based on linear regression of ln(y) vs ln(x).

My question is how does cftool compute the confidence interval of these parameters?

In the attached image the values of A,B are presented alongside their confidence interval.