[cybmole]

thanks. I added some half steps to my spreadsheet & I now thnk that the strange numbers which bug me most are from 9.5/12 (0.79167), and from 15.5/12 (1.29167)
i searched for actual examples in my library but I seem to have tweaked them all out of existence. Next time I have a source with those values in I will comment more . Pretty sure I have seen them in retail /library loan books so not sure if they are generated by publishers or by calibre conversions.
maybe it is when a publisher creates the master in some other format then uses adobe tools to make the epub, with the annoying extra xpgt templates?

I was hoping to automate conversion of the case where I see 1.29... in calibre base font, then 0.77... in all the body text css fontss ( result is 1.0 because they cancel out. mostly )