Well now I'm confused. I got the 500 coins on 10/3. Yesterday (10/8) I got an email from Amazon telling me that I got the 500 coins. Today when I looked, I saw that I had
another 300 coins.

I have no idea where they came from because I haven't bought anything on Amazon for the past several days (except for a few free apps, songs, and ebooks).
I *did* first watch a short movie extra after I first posted about this latest promotion. When the coins didn't show up quickly, I played a full TV episode to be sure. Since some people got 500 coins for watching short videos I don't see how it would have made a difference, but for those of you who got 300 coins you might try playing something longer and see if you get 500 more coins.