There ARE some serious glitches right now, however. Amazon have said 'they are aware.' This includes books listed as free 'Goodreads Giveaways' but are actually not (you are credited with payment as normal) but also unusual amounts of uncleared orders, more than can be accounted for by bad cards. They are starting to catch up slowly, about 21 of my missing books have shown up on my December month to date although they were ordered approx 1-3 days ago.
I understand the reasons the differences between the "Reports" vs. what my KDP advertising shows of book sales. However, the problem seems to be growing worse. For example, on 12/3 I sold one KDP book, then sold six more on 12/4 and 12/5. These sales from my KDP ads are not showing up on the "Reports."
The AMS ad dashboard information is NOTORIOUSLY LATE. It is almost impossible to correlate anything that happens on the ad dashboard with anything real-time.
In fact, after starting an ad, you can ignore anything that's reported in the first full week of the campaign. The info is delayed, and you can't make judgments and adjustments until the info comes in. Right now, that's the way things are, alas.