The SI prefix standard for giga- is 1 000 000 000, where as (most) software uses binary prefixes where giga- is 1 073 741 824. Thats where the "lost" space comes from. I highly doubt that drive manufacturers will change from the SI prefixes as it looks like they drives have more space, and SI prefixes are the standard for most other units of measurement. If you want to approximate the "real" storage capacity, multiply the advertised capacity by 0.926 and it will tell you about how big it will be.
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