From the wikipedia entry: "Suppose a particle (such as a photon) emitted from a source could interact with one of two detectors. According to TIQM, the source emits a usual (retarded) wave forward in time, the "offer wave", and when this wave reaches the detectors, each one replies with an advanced wave, the "confirmation wave", that travels backwards in time, back to the source." I would interpret it this way: A detector emits a wave forward in time. When a potential emitter receives the signal, it replies with another wave, forward in time as well, towards the detector. I don't see the difference between a wave going backwards in time from the detector towards the source and a wave going forward in time in the opposite direction.