an ISO is effectively an image of all the bits possible on a DVD
even if most of the bits are nothing, an ISO still contains information about them!
when transferred over to the WBFS drive, only the files are saved,which takes up less room than the space on the DVD
or, in other words, an ISO is always 4.7 gigabytes becase a DVD can hold 4.7 gigabytes of information
the files on the DVD take up much less space