Probably been asked many a time - but when there's 1024bytes in a KB and so on and so forth - Why does Plusnet round the figures down? Those missing bytes would save me from going over at the end of the month probably!
It isn't rounded down. The official meaning is the kilo, mega and giga are decimal 1000-based prefixes and kibi (kilobinary), mebi (megabinary) and gibi (gigabinary) are binary 1024-based prefixes. So 1kB (or 1KB) = 1000 bytes, 1MB = 1000kB and 1GB = 1000MB and 1KiB = 1024 bytes, 1MiB = 1024KiB and 1GiB = 1024MiB. With small sizes, the difference between decimal and binary units is small, but much increased sizes make it important to use the correct symbols. Anyone going over their decimal-based GB usage limit would have to pay 1.073741824 times more (7.4%) for a binary-based GiB limit.