quotation marks on imac

A few weeks ago, I purchased an iMac (my first ever). Now to the point - the quotation marks. To begin with, they were exactly the way I wanted, the "double arrows" that is. Perhaps I fooled a bit around with the settings, perhaps it was when upgrading to High Sierra, anyway, they suddenly changed back to the "inches" way of doing things. Why are my settings (which I believe should be right by now) overrun by something out of my control? It works perfectly on my iPad and iPhone, so I have reason to believe the double arrow should be default. Please see attached screen-shot (if it works).