What does this program print?

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

public class Main {
    static <T> void append(
            List<? super T> destination,
            List<? extends T> source) {
        destination.addAll(source);
    }

    public static void main(String[] args) {
        List<Number> report = new ArrayList<>(List.of(0.5));
        append(report, List.of(2, 4));
        System.out.println(report);
    }
}