The KiloByteSymbol in DecimalByteSize.cs (line 14) is incorrectly declared as "KB".
The uppercase "K", is considered an informal (non-standard) notation for 1024 bytes (=KiB). The correct unit prefix for 1000 is lowercase "k".
(By the way, one of the Wikipedia articles linked in the readme.md also points this out: https://en.wikipedia.org/wiki/Kilobyte#Definitions_and_usage ;-) )