The sigma that I got from fitgmdist seems small

Hi, I've used fitgmdist to fit 3 gaussians to my variable, and the sigma seems very small. The variable is attached. After histogram, the function looks:

[binsAll, centerAll]=hist(tumorFu,128);
figure;plot(centerAll,binsAll,'r');

I used fitgmdist using:

obj = fitgmdist(tumorFu,3);

and then plotted it with:

figure;ezplot(@(x) pdf(obj,x));

Although the plot looks alright and also the means, the sigma that I got is 10th more little. What do I understand wrong?