copying copies using psxcopy 6.0 image to big

Hi, I am trying to copy DC copies using psxcopy 6.0 I have succesfully burnt self booters and non self booters using this program. My problem is, some games have an image (.cdp) that is much bigger than the actual contents of the disc. for example, Zombie revenge has a total disc size of 701mb. (ascertained by looking at the properties of ther CD) but the .cdp image is much larger than this (806mb). to me this size is impossible as the game is on 80min media. I have tried using DJ and CDRwin and both give me huge image files too. Is this some sort of protection put on by the trader I use? what can I do? Any help greatly appreciated.