Splinter Cell: PT File SHRUNK!!!!!!!!

[gemini413]

hey
i have been backing-up my ps2 games for a couple of months and most of them have gone well. Yesterday, however i tried to bak up my Splinter Cell: Pandora Tommorow with dvd decrypter and there was a possible problem. My computer says that the disc is 4.27 or somethin gigs (which is about what most of my games are), but when i try to create an image and mds file on my hard drive, it writes an image that is 1.8 gigs. i backed up games both before and after using this same program and method and they have worked fine. any idea's on what the problem is??????????
Thanks for any help
also while ur here if u use ritek dvd-r's, will u please leave a link from where u get them?