[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.
`kB` is a unit not a prefix (which would be `k`). The same goes for `MB` vs `M`.