DVD burning technical question

[WelshWitchPMD]

I have a DVD burner in my PC. My question is this. If I am copying a DVD that is 120 minutes long how come it shows as a few minutes over 2 hours?
I have a blank 120 minute DVD and I kept getting an error message when I put it in to record. I finally figured it out that the DVD I was copying was over 2 hrs long but I still can't figure it out if it says 120 minutes on the front.


The DVD that I was copying was a DVD-R and the blank that I had was a DVD+R. I don't know if that makes a difference.