256 GB = 238 GiB
People get confused about their hard drive size because the OS often reports in GiB (multiples of 1024) whereas the manufacturer lists size in GB (multiples of 1000). 256000000000 / (1024^3) = 238.4, so you should expect a 256 GB drive to show 238 GiB available.
Biting the hand that feeds IT
