In this section, we'll just look at the DevPay Transaction History page so you can see how the charges for July are collected given Customer A's initial failed payment.
Starting from the bottom of the page:
The August 1 deposit corresponds to the August 1 billing of your customers for their July usage and the August monthly fees. The total billed amount includes $175.20 for the July usage and $120.00 for the August monthly fees (totaling $295.20). However, Customer A's payment of $27.20 fails. Therefore, you receive the total amount minus Customer A's payment, minus the $0.30 transaction fee per customer payment collected ($295.20 - $27.20 - ($0.30 * 6)) = $266.20.
On August 2 we charge you $258.83. This includes two amounts:
$257.59 for the cost of Amazon EC2 your customers used in July. For Customer A, we collect only the EC2 costs up to the amount of revenue we've already collected. Therefore, we collect $20.00, which is equivalent to the July monthly fee we've already collected from Customer A. The total amount of AWS costs for Customer A is $25.68, so you still owe $5.68.
$1.24 for the 3% DevPay fee on the value-add amounts we've collected from your customers (all except Customer A, whose payment failed). The total 3% fee you owe for all your customers is $1.29, but we won't collect the 3% fee for Customer A ($0.05) until that payment succeeds.
On August 7, we retry Customer A's $27.20 payment and it succeeded. We deposited $26.90 into your account ($27.20 minus the $0.30 fee).
On August 8, we charge you $5.73. This includes two amounts:
$5.68 for the remaining AWS costs for Customer A
$0.05 for the 3% DevPay fee on Customer A's value-add for July (3% * $1.52)
On August 14, you withdraw $100.00 to your bank account.
If you had decided to withdraw money from your account in June or July, it's possible the balance on August 2 wouldn't have covered the $257.59 charge. If that had been the case, we would have charged the remaining amount to your credit card. We recommend you plan ahead and leave sufficient funds in your Amazon Payments account to cover the charge for AWS costs and DevPay fees.