Fix use of KB to kB

[JPHutchins]

Use SI, including in places where the code style contradicts capitalization or spacing, in order to avoid ambiguity.

https://en.wikipedia.org/wiki/International_System_of_Units#:~:text=The%20SI%20comprises%20a%20coherent,candela%20(cd%2C%20luminous%20intensity)

kilobytes should always be kB, not KB, unless it's kibibytes, which is KiB.

https://en.wikipedia.org/wiki/Kilobyte