change Navigation bar font size for Sydney Free theme

Hi Bill Saw your https://www.youtube.com/watch?v=LPo2yfFLRa0. Helpful ! I was able to change the Font Size of the Sydney Wordpress free theme (About ... ) Using Firebug, I located the id : #mainnav ul li a in style.css Then went to Settings->Edit Font Controls-> Added a Navigation control with Override in Settings and went back to Customer->Typography->Control Name "Navigation" & set CSS Override and clicked "Save Font Control". Then I went back to Customize->Appearance->Theme->Theme Typography->Navigation ->Edit Font->Appearance I was able to modify the the Font size and do see the Web screen change the font size dynamically. All is Good. However, when I "Save and Publish" and go back to the main screen, ie to my original url eg: localhost/wordpress I still see the original font size has not changed (still very small). It seems what has happened was the steps I took worked partially only. Appreciate of you have any pointers how this could happen ? Thanks Sean