Hi @ying
The Top Ad feature creates an additional copy of your listing that appears in the Top Ad section at the top of the category. Your original ad remains in its normal position within the regular listings, so it’s completely normal to see it on page 30 or any other page. The Top Ad feature does not move your original listing higher in the regular search results.
If there are multiple Top Ads in the same category, they rotate evenly each time the page is refreshed so that all featured listings receive fair exposure.
For a more detailed explanation of how the Top Ad feature works, please see our Community article: