how to i increase a number temporally

so i have this script and i wana add running to it. i tried if input.getbuttondown but it not gona work like this. what do i do to get the number to go back to what it was after the button is released. pliz help me with ur genius knowledge in java coding plizzzz

Use `Input.GetButton()`

var value : float = 6.0;

function Update () {
     //If I recall correctly, value should snap back. other wise add another line
     value = 6.0;

     if(Input.GetButton("Jump")) {
         value = somethingElse;
     }

}