Digital River responded and said it was an adjustment for prior overpayments due to a "cost of goods sold issue" related to currency/locale after offering transactions in additional currency/locale combinations.
That doesn't explain why it affected primarily the USA payment. However, according to the report they just sent me, there was an overpayment on many USA transactions.
I haven't correlated that with the previous DR reports because the ordinary reports are not per-order like what they just sent me. The report they just sent has completely different transaction numbers from the normal DR reports.
There's something else that doesn't match -- recently on App World reports, some items look like sales tax is being charged. But on the DR report that does not show, it just shows the list price being charged. So that makes it harder to automatically correlate the two reports, when there are no order numbers on the App World report. You can't just sum all the transactions on the App World report, take 70%, and see what you should get from DR; you'd be calculating your percentage partially on locale taxes, and think you're being underpaid when you aren't.
edit: I'm still refiguring again, it's a mess!
