HUMMER Navigation Disc - Cannot burn

This is really driving me nuts. I have a 2006 Hummer with OEM Navigation. I lost my original DVD and was able to get my hands on another one to copy and return. When I pop in the DVD into my computer - the size shows up as only 178MB. When I try making a copy or image using any software (DVD Decrypter, Nero, ISOBurn, etc) it still only shows up as 178MB.

The DVD is version 5. I am sure it is encrypted in someway. I need to know how to properly see the entire data available on that disk.