Post a log (see help menu). You are probably confusing GB and Gb. Gb is 1024*1024*1024 bytes (=1,073,741,824 bytes). GB = 1,000,000,000 bytes = 7% less.
Still, DVD Shrink usually makes an image of 4464Mb (unless you changed this to 4700 for example). Something's fishy. A log will help us to help you.
Regards