While cropping an image in iPhoto 11, does "constrain" stretch the cropped area to maintain the original image size?

For example, let's say I had a 1200x1200 image and I wanted to crop a very small portion in the middle of the picture. I select constrain which shows 1200x1200 and then proceed to select the area (let's say it's very small, 25x25) and crop it without choosing a preset such as 8x10 or whatever. Will the 25x25 section I selected be cropped and then stretched to fit 1200x1200? Or is it just for maintaining dimensions? In this example a square.

Thanks for your input.