With out knowing exactly what you did makes it kind of hard to help, but I would think that maybe the the source is DVD9 in size and the disk is DVD5 (single layer). It also could be that the source is close to the maximum size for a DVD5 and the settings in
DVDFab are not set correctly (under common settings/DVD look at DVD Writeable Media for both DVD5 and DVD9). If I remember correctly the default is 4300MB for DVD5 and 8000 for DVD9.
