ISO 9906 - Type number K of the pump

[1ton]

Hi
Can some pls enlighten me on this particular subject.
Looking at ISO 9906 1999 and some previous BS for pump performance test. It is mentioned in the std, that there is a "type number K of pump"." When K > 1.2 it is recommended to simulate the site conditions"(pg 12 par 3).

Can some one explain to me.
What does K means ? How do we define K ?

Thanks