When I enter the Elder Rift and use one Rare Quest stone, I am shown 9 Fading Ember as a reward. But I only receive 1 Fading Ember. As I said, only one stone is used.
The reason why it shows 9 fading embers is because…
8 fading embers for running an Elder Rift
1 fading ember for every crest added to the Elder Rift
The reason why you’re only earning 1 ember rather than 9 is because you’ve already run 35 Elder Rifts this week and have reached the normal ember cap, but haven’t reached the bonus ember cap. As explained here, detailing why this is not a bug…