help cpsd amplitude units

have a problem with cpsd amplitude. I generate a 20s signal with two harmonic components at 5 and 10Hz, both with an amplitude of 10, then I perform the cpsd I have the two components at the right frequencies, but both with an amplitude of 1000??? it should be 100, right?

fs=512;         % sampling frequency
L=10240;        % samples
t=(0:L-1)'/fs;
x=10*sin(2*pi*10*t)+10*sin(2*pi*5*t);
[Gxx, f]=cpsd(x,x,rectwin(L),0,L,fs);
plot(f,abs(Gxx),'.r')
Where I am wrong?