Phillbo, it means pour the water into the water in the bottom of the salt tank (down the brine well, where the float is, or any other way you can but you don't remove the salt because you don't have to). BTW, you add it again after the first regeneration also.
If you pour it down through the salt, you can cause a salt bridge as the salt above the water line dries out later and sticks together; especially with the use of pellets but with crystal also.
I would leave the salt in and adding 3-4 gallons either over the salt at the edge or down the brine well.. either way will work.
But I am not sure why one would when the GE/Sears unit adds water at the start of the reg cycle.
If you where to hold off on water use for 5 hours and did 2 back to back regens that most likely will clean up the resin.
All softeners add the volume of refill (pre or post regeneration) water based on the lbs of salt to be used per regeneration.
The three gallons = 9 lbs, plus whatever his dose is currently gets him very close to 15 lbs for his usually not much more than 1 cu ft cabinet model softner.
Next to none are set to use the max of 15 lbs/cu ft of resin. So when a softener has not been regenerated properly and there is hard water breakthrough/leakage, you need to regenerate the full cuft volume of resin to it's maximum K of capacity, hence the max of 15 lbs per cuft of resin twice must be used or you don't regenerate all the resin back to max capacity. And if not then later the softener is prone to hard water breakthrough/leakage although it is operating properly.
If he doesn't add the 3 gals (= 9 lbs) the softener only uses whatever lbs of salt (K of capacity) the control valve is programmed to use and he doesn't regenerate all the resin back to maximum capacity.