PC. This was a game of brawl, deep in the late game. My opponent was at 2 life. They played a Final Parting, then an Aetherflux Reservoir, and then a Time Warp. They started their extra turn, and played an Esper Sentinel. Their Aetherflux Resevoir triggered, and they gained 4 life. They should have only gained 1 life, but it seems the Aetherflux Reservoir counted all of the spells they had cast since they started their original turn, not since the start of the extra turn.