The amount of water put back in the salt tank at the end of a regeneration with a 5600 valve is always the same volume in gallons. The volume/level of salt is always being reduced because the salt is dissolved into the water that is then sucked out of the tank as brine during the brine draw/slow rinse part of the next regeneration.
The salt displaces the water so there is no way to say if there is too much water in the tank by marking the water level and doing a manual regeneration and checking the mark. So IOW both the salt level and the water level will vary constantly.
If the softener is working right, producing 0 gpg soft water from one regeneration to the next consistently, there's nothing wrong. If the water level consistently increases the water isn't being all sucked out and there is a problem and you'll get harder water until the softener isn't removing any hardness.