DVD seems to get bigger?

Ok here’s another I cant copy a dvd problem.

I have lots of home movies on tape and camera tape. But I want a more permanent source that wont degrade as much. So I decided to put the onto dvd.
The best way I figured was to put them on using a friends dvd recorder.
His recorder only supports DVD+R/RW and I only have DVD-r disks so he copied from:
Hard drive-> DVD+RW->Computer hard drive-> DVD-R
The disk is a standard 4.7 GB DVD. windows says the content is 4.29G
but I cant copy it (as now friends want it because there on it)
The reason I mention the size is:
Nero copies the disk, but wont write it to a cd, it asks for a bigger DVD
DVD Decrypter & DVD fabDecrypter(used because of these forums) Copy it to hard drive as 6GB
Magic DVD ripper(suggested by forum) says backing up will take 6 GB
Also drag and drop copy increases the file to 6GB.
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Then there’s 1 I shouldn’t have to try, but did. DVD Shrink. This opens the file and if I turn the compression off correctly shows the file size. However clicking on backup gives the error “programming error – exception occurred” If I try backing up the 6GB copy of the file I get an “invalid data in file” error. Anyone know what’s wrong here.
Thanks