That depends on how many people are in the household and how many eggs they like to eat. There is no perfect number that will work for all situations.stick with your 4 -- that is literally the perfect number of hens for daily egg usage. Once they begin laying you will get 1-4 eggs a day and that is literally all you will ever need.
In this case I agree that OP should stick with the four pullets and not add more, but I say that because of the coop size not because of how many eggs will or will not be produced.