You specify the main URL as the search engine could possibly have trouble pinpointing which 1 need to be the main URL.  The next tutorial will tell you about the best way to allow Canonical URLs in Prestashop 1.5. PrestaShop modules we produced initial to solve the trouble of https://addons.prestashop.com/de/seo-suchmaschinenranking-optimization/31857-automatische-google-rich-snippets-json-ld-opengraph-seo.html