Bing is now testing “Top Pick” badges within Shopping ad results. Along with the badge, the box for that particular result appears larger compared to others.
I think this “Top Pick” badge might be based on past user behavior how often users have clicked on or purchased a particular product for a given keyword and it could reflect the best-selling item for that specific search term.
Here is a screenshot of how it looks.

Showing a badge with a larger box for a specific product could help increase CTR, giving that website a visibility boost over competing results.
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