so if you mount it to a Mac it will in fact say you have 64GB but on a windows machine it will say about 60GB
But a file that is 1 MB on a computer that uses (2^10) measurements will be 1 048 576 bytes on a computer that uses the (10^3) measurement. So in the end you can store the exact same amount of data, no matter which computer you use.
Right, it's a matter of perception. They decided to do that because people don't understand the conversion..and since HDDs are now rated in GBs people get confused when they buy a 500GB hard drive and see it actually only has 488GB (because they didn't buy a 500GB hard drive they bought a 500,000MB hard drive...as stated in the fine print.)
Now that drive will come up as 500GB...you haven't actually gained anything you are just viewing it differently.
Like when people installed SL the first time a lot of people thought they gained about 30GB of space....it was all in how it was displayed...SL was a little slimmer than leopard...but only by a couple GB.