I should have posted the image of the page when I asked the question, so here it is.
I gather from the text that 'propeller power required' is that power needed to maintain the propeller rpm from that which is produced for a given throttle setting in ISA conditions, when moving into non-ISA conditions.
Thanks for your interest
Last edited by roadrabbit; 22nd Jun 2016 at 09:43.
Reason: clarity