If you start with a pound of potatoes, by the time you've peeled them, boiled them and mixed up all the other ingredients, you should have about a pound of potato salad.
I use about four large potatoes and if they are small about six. Once peeled diced, cooked and all ingredients, such as hard boiled eggs, vegetable, would be about 2 lbs
What are the other ingredients you are adding
"If" it is only Potatoes then 1 pound
If others add there weight then the rest potatoes
and 3rdly why not follow the recipe?