problem copyong dvd

hi guys
i have a problem making a back-up of a dvd.
while trying to copy through various software. computer says disk is 6.41gb but when i open disk it becomes 54.8gb ?
now i realise this cannot be possible is there a new encryptor that is doing this ?
i have tried this on 3 computers same results each time
any help or ideas
thanks

dvd is a christmas carol
hope this helps

Try this: SlySoft Products | Copy Movie DVDs with AnyDVD and CloneDVD. There is a trial period first and if it works for you worth buying. Good luck.