It does not only scan 3000. From the source code:

      const portsToTry = [
        80, 81, 88,
        3000, 3001, 3030, 3031, 3333,
        4000, 4001, 4040, 4041, 4444,
        5000, 5001, 5050, 5051, 5555,
        6000, 6001, 6060, 6061, 6666,
        7000, 7001, 7070, 7071, 7777,
        8000, 8001, 8080, 8081, 8888,
        9000, 9001, 9090, 9091, 9999,
      ];