I think it was your thread
https://www.mobileread.com/forums/sho...-before&page=2
Look at posts 30 thru 33. The space was intended to force ADE to jump the "page number" up to the next digit.
I don't know that that is such a critical issue, depends on which you consider worse: A page number repeated, or the top of page mis-aligned.
You could always just split the file at each new page-break, and have multiple small files.
(I do that after I have completed
all editing with the book in a ginormous single file)