SNR and AWGN Question

Hi everyone, I have a question regarding the swgn function. I have a rectangular pulse of magnitude 1 Volts, starting at t=10s for the time period: t=[0:0.01:60] seconds. I want to add a white Gaussian noise of SNR=10 dB to this signal. I use the following comands:

time=0:0.01:60;

i=1;

t=0;

while t<=60

    if t>=10
        V(i)=1;
    else
        V(i)=0;
    end
    i=i+1;
    t=t+0.01;
end

Vnoisy = awgn(V,10,'measured'); % Add white Gaussian noise.

plot(time,Vnoisy)

After executing these commands, the maximum of the Vnoisy is 2.0737. In other words, the maximum noise is 2.0737-1=1.0737 Volts. This results in an SNR of 20log(1/1.0737)= -1.422 dB not 10 dB.

Could you please guid me in the right direction?

Thank you!