question about SI/IEC in df

[Krzysztof Labus]

In the manual I see:
The SIZE argument is an integer and optional unit (example: 10K is
10*1024).  Units are K,M,G,T,P,E,Z,Y (powers of 1024) or KB,MB,...
(powers of 1000).

1. Why df not using Ki, Mi, Gi etc. in powers od 1024 ??

2. On my computer: df -H print:
-----
none        _504k_     0  _504k_   0% /dev
-----

df -H
-----
none        492K     0  492K   0% /dev
-----
I see the difference in the presentation of results and what is in the
manual -> (...) KB,MB,... (powers of 1000) (...) but df -H print small
letter k


Best regards.
Christopher Labus