为什么这个月亚马逊订阅服务费只扣了23.65美元？而不是39.99美元？

我收到邮件说：

We have charged your credit card for $23.65 in an attempt to settle your Amazon seller account balance.

Note that the amount charged to your credit card may be less than the total amount you owe due to a credit limit imposed by your bank. If that is the case, we will continue to charge your credit card as often as every 24 hours until the remaining balance in your Amazon seller account is paid in full.

我看了下我的账户，我的后台美元显示欠款，而且显示已经支付了23.65美元给亚马逊，我想问一下，是这个月的月费就是23.65美元么？如果是的话，为什么？还有，我到底还欠钱么？我看不懂。