Three months ago we launched a bill installment feature. Product says it is a success: 8 percent adoption and 200 million dollars in installment balances. But Risk found that those customers' revolving balances dropped by 150 million. If you had to define the success metric for this feature, what would it be?

我们三个月前上线了「账单分期」功能。产品团队说使用率8%、分期余额2亿美元，很成功。但风险团队发现，用分期的客户原来的循环余额少了1.5亿。如果让你给这个功能定一个成功指标，你会怎么定？