The rect parameter given to imcrop is [xoffset yoffset xwidth ywidth]
I = imread('https://www.mathworks.com/matlabcentral/answers/uploaded_files/996600/2_mask.png');
I2 = imcrop(I,[739.72-32 406.02-32 64 64]);
imshow(I2)
... although you may find out that you have to subtract 1px from the widths if you actually want a specific output size. This behavior is explained in the help for imcrop().
I2 = imcrop(I,[739.72-32 406.02-32 63 63]); % this will be 64x64 instead of 65x65
