Calculate actual disk size in Windows
ref: https://linustechtips.com/topic/1376340-why-only-475gb-on-a-512gb-ssd-on-a-lenovo-laptop/#comment-15013106
512G
512,000,000,000 / 1024 / 1024 = 488,281.25 MB / 1024 = 476.83 GB
use 475GB (486406MB) for C drive
256G
256,000,000,000 / 1024 / 1024 = 244,144 MB / 1024 = 238GB
use 235GB (240646MB) for C drive