Why do the "burn marks" not show on some DVD-R's I

[Sominex24]

I have noticed something odd.

Someone made a DVD-R on their PC.

They gave it to me to make copies


When I look at the bottom of it, it shows no "burn marks" like a typical CD-R or DVD-R. It is purple all the way through out.

Why is this?

[jaxxboss]

maybe if the burn was a full disc burn u wouldnt notice it as the whole disc was used and u cant tell.