Scope displays keywords for products that rank within the first 4 search result pages when each keyword is searched. If a product is not included in those first 4 pages, nothing will be displayed.
Amazon only indexes the first 250 bytes in a product detail page’s backend keywords. A keyword may also be indexed from the title or bullet points. Please keep in mind that just because a product is indexed for a keyword, does not necessarily mean the keyword also ranks for a product.
You can confirm if your product or a competitor’s product is indexed for a specific keyword by running a reverse ASIN lookup. If the ASIN is indexed for this keyword, it will then be displayed on the search engine results page.
If it isn’t indexed, say for example I search for B00XTCERLE+manzana, the search engine results page will say “Your search “B00XTCERLE+manzana” did not match any products.”
You can learn more about indexing your product on the Seller Labs blog here.