发case给客服，客服说是由Website Display Group (wdg) 决定的，以下是客服的回复

Hello from Amazon Selling Partner Support,
From your email, I understand your concern regarding sales rank for the ASIN's: ~，~，~. I understand how frustrating it would have been for you, please be informed, I'll look into it to provide a timely resolution. Before we proceed further, kindly accept our sincere apology for the inconvenience borne by you. In this regard, please be informed that not all ASINs are eligible for sharing ranks. The criteria for this eligibility cannot be shared. Please know that we don't update sale rank manually it's a automated process by the system. Furthermore, variations handling depends on the Website Display Group (wdg) of the parent ASIN. In some stores, we add up all the sales for a child ASIN and apply it to the parent ASIN. In these stores, parent ASINs and child ASINs will have the same rank. In other stores, we count the orders for each child ASIN separately and generate sales rank for each child ASIN. Ensure that your child and parent ASINs are assigned to the same website display group, and the parent ASIN has the right browse categories assigned to it or you might not see a sales rank for the same. For more information regarding this please go through the bellow mention help page: Sales Rank FAQ: https://sellercentral.amazon.c ... 59240 Your patience and understanding in this matter are highly appreciated. It was a sheer pleasure assisting you today. Please let us know how we did.

我担心这种情况会使权重分散在每个子体，不会聚集到一个父体上，从而很难推。
跪求怎么实现子体排名相同，或者说将各子体的权重聚集到父体上，实现排名相同。