WHY THERE IS DIFFERENCE BETWEEN ACTUAL CAPACITY AND MARKED CAPACITY OF SSD?
This is due to a unit capacity conversion issue. Hardware manufacturers usually define 1K=1000 bytes according to decimal, while software providers (ex: Microsoft) define 1K=1024 bytes according to binary.
In addition manufactures retain 3~5% of capacity for firmware, application software, and data storage maintenance. So there is a difference between actual capacity and marked capacity.