Currently the base of binary units in most (all?) plugins, e.g. check_disk which use them seems to be 1024.
This is though usually not documented, which makes the whole thing ambigous.
Please support SI units and use the correct units:
First that means that things like kB, MB or --megabytes of e.g. check_disk should no longer use the incorrect basis 1024.
k is always 1000, etc. pp.
The IEC standardised the use of e.g. KiB, MiB, GiB, TiB as units with the basis 1024.