You specify the main URL because the online search engine might have problem analyzing which a single really should be the primary URL.  The subsequent tutorial will tell you about how you can help Canonical URLs in Prestashop 1.5. PrestaShop modules we established initially to solve the challenge of https://addons.prestashop.com/pl/seo-pozycjonowanie-naturalne/31857-automatyczne-google-rich-snippets-json-ld-opengraph-seo.html