Rev. A 64GB SSD shows up as 59.68GB in Snow Leopard?

Hi,

Sorry I wasn't sure whether to post this under OS X or MBA forum but settled on this one in the end. Also I searched but couldn't find anything so hopefully this isn't posted anywhere else.

I have a Rev A MBA with the 64GB SSD, and am just wondering why it shows the capacity as ~60GB under Snow Leopard, when I'd thought it was supposed to show the capacity as it is marketed as, ie. as 64GB? I read somewhere that there is also some capacity taken up by partitioning, but doesn't 4GB taken up by partitioning seem like a lot? I just thought I should ask since I don't really understand... I found another thread but then it seemed like the person only lost 1GB due to partitioning, and that was on a 1TB drive, meaning they were loosing far less of the drive's capacity as a % than I seem to be.

Finder shows the capacity of my SSD as 59.68GB, System Profiler as 60.02 GB (60,022,480,896 bytes), and Disk Utility as 60.02GB.

Thanks

EDIT: just to make it clear I understand all the base 10 vs. base 2 stuff, it's just that under base 10 in 10.6 I don't understand why my SSD doesn't show up as 64GB.

cool thanks for explaining obviously in Leopard it showed less than 64GB (and less than 60GB) but I'd always assumed it was just because of base 2 thing and didn't think any more of it (and the same with my iPhone - although of course that doesn't run Leopard/Snow Leopard but you know what I mean!).