[Reference] fix from suffix to prefix

| Q             | A
| ------------- | ---
| Doc fix?      | yes
| New docs?     | no
| Applies to    | 2.6+
| Fixed tickets | 

As @Tobion said in #3895 and like the Wikipedia article describes, the handling of *prefixes* (not suffixes) was introduced.
`Ki` is a prefix, `KiB` is a unit. Same goes for `Mi` and `MiB`.