Object Reference and ArrayList Modification

Consider the following NumberList class and main method.

public class NumberList {
    private ArrayList<Integer> numbers;
    
    public NumberList() {
        numbers = new ArrayList<Integer>();
        numbers.add(10);
        numbers.add(20);
        numbers.add(30);
    }
    
    public ArrayList<Integer> getNumbers() {
        return numbers;
    }
    
    public void addNumber(int n) {
        numbers.add(n);
    }
}

public static void main(String[] args) {
    NumberList list = new NumberList();
    ArrayList<Integer> nums = list.getNumbers();
    nums.add(40);
    System.out.println(list.getNumbers().size());
}

What is printed when the code segment is executed?