For each extracted line Sprwt first looks for an ingredient already mapped to that supplier with the same supplier item number (product ID). If none, it compares the line name with all ingredient names: an exact name match wins, otherwise the closest name with at least 75% similarity. Matched lines go to Existing Items; the rest go to Non-existing Items. When you reopen the review page, new items are re-checked against ingredients created in the meantime. If a match is wrong, click the pencil (Change ingredient) next to the linked name on the card and search for the right ingredient.