A Search Listing page shows multiple products, like a Category page or a Search Result page. Implementing Criteo OneTag on these pages allows Criteo to track the user's interest in a certain kind of products (e.g.: products of a particular category).
You can find detailed instructions of how to to use the Criteo OneTag on your Search Listing pages here.
It is strongly recommended that you pass the top three product IDs within the Criteo OneTag on the Search Listing page. Alternatively, you can pass three product IDs of products shown on the page.
More than three product IDs are being passed
If more than three product IDs are being passed, Criteo will only take the first three supplied IDs into account. For maximum performance it is recommended that you only pass three IDs.
Less than three product IDs are being passed
If less than three IDs are being passed, Criteo cannot analyze the user's intent correctly; this will negatively affect the performance of your campaign. Therefore, you should always pass three IDs into the Criteo OneTag.
The only exception to this rule would be for a search result that returns less than three products.