They used to have a highly proprietary Fleck 5600 but it sounds as if you may have a 5600 with an SE timer. Go to
www.Fleckcontrols.com and look at some pictures to find out what valve and timer you have.
Then get hardness, iron and pH tests if you are on your own well, if not get the highest hardness data from the water company's web site and use it.
Then you need to tell us what size softener you have by measuring the width and height of the resin tank or looking for a model number on a label on the straight sides of the tank; a model 948 means 9' x 48" tank and that is a 1.0 cuft softener.
Then tell us how many permanent residents live in the house.