idiot 5.3 disk question

[thursday]

Greets,

I haven't been following FreeBSD much at all lately, having gotten a Linx admin job, so forgive me:

I'm installing FreeBSD 5.3 on a new machine. I've added a second disk, and 80Gig Maxtor IDE drive. I use sysinstall to partition it, and run disklabel/newfs, etc, mounting it as "/storage". 

In sysinstall, it shows the disk as being 78G - that's fine. 1024 != 1000. 

However, when I run df -h it tells me the disk's capacity is 74G, there's 4.0K in use (it's empty), but only 68G is available. I'm just confused about where the 12G went. 

Anyone have any helpful pointers to help me understand? 

Also, what's the ".snap/" directory for? 

Thanks so much!