|What do you mean by reserve areas? |
The stated manufacturer's size is the "raw" size. Some of that capacity is used up when the drive is partitioned and formatted.
The manufacturer's stated size is often expressed in decimal gigabtes rather than binary gigabytes which are what most if not all bioses and all operating system use (at least, they always do that with hard drive sizes). It often isn't exactly decimal xgb - that varies a bit, fractionally, usually upwards.
I have a Kingston Traveler "2gb" flash drive, it's FAT partitioned and formatted - the total space usable for data is 1.90gb (2,047,803,392 bytes) binary.
I have a Kingston Traveler "4gb" flash drive, it's FAT32 partitioned and formatted - the total usable space for data is 3.72gb (4,000,825,324 bytes) binary.
Similar applies to memory cards.
1 decimal gb = 1,000,000,000 bytes = 1 billion bytes
1 binary gb = 1,073,741,824 bytes = 1,024 bytes / kb x 1,024 kb / mb x 1,024 mb / gb
2 binary gb = 2,147,438,648 bytes
~500gb decimal = ~465.66gb binary