I have upped my spending in Amazon Ads to equal whatever I sell each month, trying to put more into ads over the long haul. But, something happened yesterday that made me wonder what the hell Amazon is doing. For most of the month, my sales on the AMS page showed $0.00 and then around the 20th there was a sale that showed up in the table for $3.99. Then that's where the Sales column stayed for the next nine days. Ad spend kept going up and I was getting some page reads with a sprinkling of "sales", but still it only showed $3.99 in the sales column.
Then, yesterday the sales column exploded, showing an increase of over eleven times what it showed the day before. However, the reports page for KDP doesn't show even half the amount the Ads page does. I was under the impression that borrows didn't show up in the Ads sales column because that's the only place I can think of where the extra "sales" have come from.