Determining a value to a cell with potential multiple options

I am working on a project in which I need to determine the number of possible residents can attend a particular school. The issue I am running into is when a zip code has multiple school options. In those cases the number of residents will be divided amongst the number of schools. Example - 2,000 residents - 4 schools - each would have 500 next to their name in the summary section featured below the data. There are occurrences where it can be up to 7 potential schools for a particular zip code. I have attached an example of what I am trying to accomplish. Thank you.