The issue is in your software that displays the capacity (most likely windows).
You bought 2 TB SSD. You got 2 TB SSD. This is equivalent to 1.8 TiB (think of it like yards and meter). Windows shows you the capacity in TiB, but writes TB next to it.
Say you buy a 2.18 yard stick. You get a 2.2 yard stick, which is equivalent to 2 meter. Windows will tell you it’s 2 yards long. Why? I don’t know.