How does one check the promotional credit balance? I thought it may be this
link, but it shows credit for video/mp3 and zero for kindle editions. Perhaps kindle editions does not mean ebooks and the credit for mp3/video also works for ebooks?
And does 'select ebooks' mean that that the credits don't work for some ebooks? The problem here is that when you purpose ebooks, there is no summary screen before the actual purchase but it goes through 1-click. So there is no way to check if the credits are applicable or not. I recently bought an ebook and noticed later that my credits were not used, which was a first for me.