Normally I ignore this tab except to choose the page number location that I prefer for the book.  If you are furnishing a printer with camera-ready copy, then you may prefer one of the Alternate choices.  If this is the case, you probably want the Odd Right option.  If you do choose an Alternate option, be sure that sections/chapters all start on the proper page – meaning you may need to include a blank filler page in some cases.