OS 10.4 - Folder/File Size Use Discrepancy

Hi, I just recently purchased another external hard disk (500GB Seagate) to backup my existing external (250GB Seagate) and came across something odd as I finished copying everything to the new drive.

The original drive was divided into two partitions, which I simply named "Seagate 1" and "Seagate 2"
I copied all the contents of "Seagate 1" to a folder named "Seagate 1" on the new drive and all the contents of "Seagate 2" to a corresponding folder named "Seagate 2" on the new drive.

Now, when I check the sizes of the two partitions on the original drive (Seagate 250GB), they are "83.5GB on Disk" (Seagate 1) and "86.47GB on Disk" (Seagate 2).

However, when I check the corresponding folders on the Seagate 500GB drive I have copied everything to, the sizes are 76.99GB on Disk for the folder containing the contents of Seagate 1 and 77.84GB on Disk for the folder containing the contents of Seagate 2.

Something else I have noticed is that if go into the drive in Finder, highlight all folders in the drive, and click "Get Info" (as opposed to just clicking on the drive and clicking "Get Info") the file size of the contents of the folder is now 76.99GB on Disk and 77.84GB on Disk, respectively.

I am thinking this discrepancy is arising because of hidden files/folders on the drive, but I am not sure. If anyone here has any more info, it would be greatly appreciated as I must format the old drive to HFS+ (currently is in NTFS).

Also, what are the "Recycled, Recycler, and System Volume Information" folders doing on my drive? I have never seen these before using my drive on OS X.

-MacBook White C2D 2.0GHz
-2GB RAM
-80GB HDD