Blast, their rep mentions "A more "typical" shaking of the purifier will generate a brine concentration ranging between 60 and 80 g/L" That sounds like the base concentration and then the electrodes run power through them until the set dosage/concentration is sensed. They mention it is not time based because the amount of shaking changes the NaCL concentration and thus both the current resistance and the amount of salt available for reaction.

Perhaps it measures initial resistance and calculates the "low salt" message from that... Once it gets above it's threshold, it fires up, and based on dosage, probably just stops when the resistance changes by a certain percentage. Perhaps a multimeter would be helpful in this rig to get a good idea of the time/concentration ratio needed for a given volume of untreated water.