[VAIO_PC] The hard disk/SSD capacity differs between OS, BIOS screen and catalog

When I check the capacity of my HDD or SSD in Windows, the BIOS setup Menu, or the product catalog, I get different results. 
There are differences shown because the capacity is dependent on how it is calculated
 
Applicable Products
All VAIO PC
 
Description
The difference exists because the hard drive space is calculated differently in catalogs and Windows.
 
On catalogs and specs, 1KB = 1,000 byte (1GB=1,000,000,000 byte).
In Windows, 1KB = 1,024 byte (1GB=1,073,741,824 byte).
The graph below shows how size differs based on the difference in the calculations above.
 
 

 
Disclaimer:
If there’s recovery space in the hard drive, the displayed capacity for the C drive will be the amount above minus the recovery space.  Along with recovery space, the displayed capacity for the C drive for PCs with “Rapid Wake” will be the amount above minus the space for Rapid Wake.  The amount of space depends on usage.
 
Reference:
The actual size is 1KB=1,024 byte, but for simplification, it is calculated as 1KB=1,000 byte. It is customary that hard drive makers calculate the hard drive capacity as 1KB=1,000 byte.