Type B and C RCBO's together?

[Farmelectrics]

is the 80% value the one out the regs and the other out of osg seems daft to me having two different values what do they mean by the 80% value please explain

 

[pushrod]

is the 80% value the one out the regs and the other out of osg seems daft to me having two different values what do they mean by the 80% value please explain

BS7671 gives Zs values at their max operating temp so if you are taking the reading at a lower temp you would want a lower value.(Resistance increases as temp increases) It can be calculated accurately or you can use "the rule of thumb" approximation and take .8 of the value for readings at normal temp. The OSG in appendix 2 gives its readings as if the temp was 10 celcius and table 2E in the OSG gives correction factors for other temps.
The R1+R2 values in App 9A of the OSG are given for 20 celcius and table 9B gives correction values for other temps - you do get used to it in time