file size issue

I've noticed something: when I use 'view info' on files on my usb memory stick, the file size is much bigger than when I use it on the same file on the desktop.

For example: I've got a gif file on my memory stick. Using 'view info' on that file it says:
Size: 32 KB on drive (7.129 bytes)

When I copy that same file on my desktop it says:
Size: 8 KB on drive (7.129 bytes)

Which makes more sense.

Why does it give 32 KB for a 7.129 bytes file when I vied the info on that file on a usb memory stick? It does that with all files on usb drives. The 7.129 bytes in this case seems to be the true file size, but for some reason 'view info' adds a significant file size to it. Can anyone explain this?