The Amazon Best Sellers calculation is based on Amazon.com sales and is updated hourly to reflect recent and historical sales of every item sold on Amazon.com.
While the Amazon Best Sellers list is a good indicator of how well a product is selling overall, it doesn't always indicate how well an item is selling among other similar items. Category and subcategory best seller lists were created to highlight an item's rank in the categories or subcategories where it really stands out.
We choose a few of the most popular subcategories in which the item has a high ranking in relation to other items in that subcategory, and showcase the item's rank on the product page. As with the main Amazon Best Sellers list, these category rankings are based on Amazon.com sales and are updated hourly.