6Gb from 4.7G DVD

I have a DVD (+RW) I've recorded on a home DVD recorder (Bush DVHRS02 combi DVD recorder-VCR).

I want to make a copy of it using my PC so I copy the filesystem to PC HDD in order to burn onto a new DVD. However it's occupying approx 6G on the HDD! It's definitely from a 4.7G DVD+RW.

$ ls -l * VIDEORM: total 1096 -rwxrwxrwx 1 john john 2048 1970-01-01 01:00 CHPTDF.DAT -rwxrwxrwx 1 john john 32768 1970-01-01 01:00 VIDEORM.BUP -rwxrwxrwx 1 john john 1048576 1970-01-01 01:00 VIDEORM.DAT -rwxrwxrwx 1 john john 32768 1970-01-01 01:00 VIDEORM.IFO

VIDEOTS: total 6313964 -rwxrwxrwx 1 john john 12288 1970-01-01 01:00 VIDEOTS.BUP -rwxrwxrwx 1 john john 12288 1970-01-01 01:00 VIDEOTS.IFO -rwxrwxrwx 1 john john 393216 1970-01-01 01:00 VIDEOTS.VOB -rwxrwxrwx 1 john john 100352 1970-01-01 01:00 VTS010.BUP -rwxrwxrwx 1 john john 100352 1970-01-01 01:00 VTS010.IFO -rwxrwxrwx 1 john john 1073676288 1970-01-01 01:00 VTS011.VOB -rwxrwxrwx 1 john john 1073676288 1970-01-01 01:00 VTS012.VOB -rwxrwxrwx 1 john john 1073676288 1970-01-01 01:00 VTS013.VOB -rwxrwxrwx 1 john john 8126464 1970-01-01 01:00 VTS014.VOB -rwxrwxrwx 1 john john 100352 1970-01-01 01:00 VTS020.BUP -rwxrwxrwx 1 john john 100352 1970-01-01 01:00 VTS020.IFO -rwxrwxrwx 1 john john 1073676288 1970-01-01 01:00 VTS021.VOB -rwxrwxrwx 1 john john 1073676288 1970-01-01 01:00 VTS022.VOB -rwxrwxrwx 1 john john 1073676288 1970-01-01 01:00 VTS023.VOB -rwxrwxrwx 1 john john 8126464 1970-01-01 01:00 VTS024.VOB

The VTS02* files would see to be duplicates of VTS01* (I diffed the first of each 1G files), though just omitting these from the copy DVD results in something the machine won't play.

I'm curious how the original c. 3G-worth of data on the DVD looks like 6G worth to the Linux filesystem: oresumably this is a function of how the recorder writes the filesystem's index files (mount shows the DVD mounted as type 'udf' whatever that is).

Also I'd be interested to know how I can copy-backup DVDs (under Linux, Kubuntu).