My HDD / SSD has less space than specified. What is the reason for this?
This is not a production defect, but the different information is caused by the use of two different numeral systems. Once the numeral system with which the manufacturer handle (decimal system) and the numeral system with which computers handle (binary system).
While the decimal numeral system works with the base 10, digits from 0 - 9 and the conversion factor 1000, computers work with the binary numeral system. In the binary numeral system the conversion factor is 1024, which produces a different result.