[userbinator]

NAND flash is... weird. The old generation of SLC and MLC flash actually had more than the binary size, with the extra being used for error correction and wear leveling information. Newer MLC has larger "spare area", but is sufficiently unreliable that SSDs tend to round down the binary size to a decimal number and use the difference for replacing bad blocks as they wear out and fail.

TLC flash has a capacity that's actually a multiple of 3 times a power of 2, with an additional spare area. I believe a "128GB" TLC SSD might have somewhere around 150GB of writable bits.