Quick question on default html directory in config.

I have a new digital ocean Ubuntu 18.04 machine and I thought I overrode the default html directory for error pages and content as per config attached to /var/www/html but for some reason the index.html ONLY is being pulled from /usr/share/nginx/html. I only figured that out from a nginx -V command and checking directories. Oddly enough the 500 server error page DO come from /var/www/html. Little help here? Can't see why this only works for some content and not all.

In /var/www/html I've got 404.html 40x.html 50x.html FavIcon.ico index.html info.php robots.txt sites.html