[X-Newbies] Carbon Copy Clone question?

[Gen Hadlow Mac Impact Dbn]

I have a friend who is using a G5 with 2 x 160Gb hard drives. One drive is
his normal drive and the second is used just for backing up the first drive.
He used Carbon Copy Cloner to copy the first drive exactly onto the second
back up drive. Everything seems to be in order and there when he looks at
his files except that the first drive shows that there is only 9.5 Gb of
free space left and the second drive has 35.5Gb of free space!
If one goes to the system profiler it shows that the main drive is formatted
Journaled HFS+ and the second back up drive is only HFS+ (no Journaled)

Is there any explanation for this?

Gen