PS2 Backup Creation question

I am using nero 5.5.10.50. When I tried to copy my Xenosaga disc everything was running smoothly until needed to insert blank media for the copied data. I tried to use a Fujifilm DVD+R 4.7 GB disc but Nero told me that the blank wasnt big enough. What am i doing wrong and how do i successfully create a backup of my game?

Come on mate, you know that backup discussion isn't allowed.
Luckily i'm in a good mood, but continue then you'll just end up banned.