Wildcards

What will be the result of the following code compilation and execution:

import java.util.ArrayList;
import java.util.List;

public class Application {
  
  public static void main(String[] args) {
    System.out.println(wildcardsTest(new ArrayList<>()));  
  }
  
  public static Object wildcardsTest(List<? super Object> numbers) {
    numbers.add(10);
    return numbers.get(0);
  }

}