lol not to be harsh or anything but did you read my post??
Just like a hard drive or something. Straight out of the box, go out there and find me one that will give you the exact amount of space they say. Completely wiped out hard drives with nothing on it are still not their exact 320gb or w/e. I'll be honest, i don't know the exact reasoning behind this and never really cared to learn about it but for all the years i've been building computers. I've yet to receive a hard drive that i bought which is stated to be 500gb actually come with 500gb. It's always like 480-490gb or something.
Same seems to go for phones, PMP's, etc...My iPod touch which is 8gb (got the first gen the day it was released) did not come with 8gb of storage for me to use. Of course there is the OS and stuff already pre-installed but it came in at around 7.6gb with the OS and default apps. Though this argument isn't as good as the PC Hard drives, it still kind of makes sense.
The test device could have a number of things we can't account for, maybe the person put some songs on it? so it came out to 6.6gb. Either way, im just gonna say. It's like a PC Hard drive and you won't get the full 8gb stated, you will get less even if it is completely wiped out and i have no clue why, it just is, i just never thought much about it all the years i've been building computers and frankly, i still don't really care.