Calculate MSE and PSNR

I have develop a steganography algorithm in C#. Now I want to analysis of my cover image and Stego image (After steganography apply). So i want to calculate MSE, PSNR of these image. I found a code here http://www.mathworks.com/matlabcentral/answers/81048-mse-mean-square-error. Is that is ok? But when i run this code i have the following output

I want to know what the output actually mean.

Thanks in advanced.

[Karbala'a Unvi. Science]

that is because you are using an RGB image not a gray level one. You will say how do I know that? I had the same message, then I checked my code I found that each value is for a color band of the color image. When you change your images to gray it will gives you one value... Yours Z