I don't have Bob's book to hand so I can't check just now.   However, the relevant place to get the answer to your question is the horse's mouth CASA booklet ("RPL, PPL, and CPL (aeroplane) Workbook") which you can download from RPL, PPL & CPL Workbook - 2 December 2021 CASA - amended 11.10.2021 

Always make sure that you are using data from that booklet and note the red line at the bottom of each page "FOR EXAMS FROM 2 DECEMBER 2021 ONWARDS".  Be aware that there will be older (different) versions floating about.   

Same thing applies with the Alpha trimsheet.   The original sheet was designed by Norm Overmeyer around 1979 and applies to the Piper Turbo Lance II, if I recall correctly.   Norm's sheet was hand-drawn as we didn't quite yet have computer graphics programmes at that stage.   The examiner subsequently got Bruce Clissold to redraw it with a graphics package to make it a bit prettier.   Both versions are about and, if you use the original, it will give you "slightly incorrect" answers for exam questions.

Thank you John for your comprehensive reply which explains it all well! I was not aware of the casa resource quoted. 

Bob tried extremely hard to cover all bases and produced some pretty good training material.   However, there is heaps of useful stuff on the CASA site so you are well advised to spend a bit of time wandering about in it.