Android : onsaveinstancestate only works once?

I have an app with two layouts (portrait and landscape). There are 4 int values I want to save so they don't get erased on rotation. For that, I call on save instance and then I recover the state on the onCreate method like this:

 private int operando1;
    private int operando2;
    private int operador;
    private int contadorIntentos;

    private String operadorTxt;
    private static final String CONTADOR_INTENTOS = "contadorIntentos";
    private static final String OPERANDO1 = "operando1";
    private static final String OPERANDO2 = "operando2";
    private static final String OPERADOR = "contadorIntentos";


    @Override
    protected void onSaveInstanceState(Bundle outState) {
        super.onSaveInstanceState(outState);
        outState.putInt(CONTADOR_INTENTOS, contadorIntentos);
        outState.putInt(OPERANDO1, operando1);
        outState.putInt(OPERANDO2, operando2);
        outState.putInt(OPERADOR, operador);

    }




 @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_actividad_principal);
       //other random code
        Random generador = new java.util.Random();


        if (savedInstanceState != null){
            contadorIntentos = savedInstanceState.getInt(CONTADOR_INTENTOS);
            operando1 = savedInstanceState.getInt(OPERANDO1);
            operando2 = savedInstanceState.getInt(OPERANDO2);
            operador = savedInstanceState.getInt(OPERADOR);
        }else {
            contadorIntentos = 0;
            operando1 = generador.nextInt(1000);
            operando2 = generador.nextInt(1000);
            operador = generador.nextInt(4);
        }

Well, it turns out that it only saves the state once. after the first rotation (when it saves correctly) if I modify things and rotate again it recovers the state of the first rotation. It's like onsaveinstancestate only works once. Why?