not able to burn from toshiba xs32 burning to -r dvd 6hr

I have set up my tosihiba to 1.4 which is the lowest recording for the hard drive and dvds and it says I can put 6 hr and 19 min on a disk but when I try to burn I get around 4 hrs.


Any help would be appreciated. Rather than record on my directivo and burn to dvd, it is nicer with the dubbing which is quicker.