My girls have taken 1/5 of a teaspoon of table salt per day since the day they were born. I just measure out the 1/5 tsp into a little jar each morning and then each feeding, I put a little in. It isn’t really important that she get the same amount each feeding, just as long as she gets the full amount each day.

If you are using the liquid sodium chloride from the pharmacy, use the same reasoning--some in each bottle.