Why is there a duplicate target 5 in this challenge?

I’m currently doing the “Clone an Element Using jQuery” challenge.

The code is as follows.

<script>
  $(document).ready(function() {
    $("#target1").css("color", "red");
    $("#target1").prop("disabled", true);
    $("#target4").remove();
    $("#target2").appendTo("#right-well");
    $("#target5").clone().appendTo("#left-well");

  });
</script>

<!-- Only change code above this line. -->

<body>
  <div class="container-fluid">
    <h3 class="text-primary text-center">jQuery Playground</h3>
    <div class="row">
      <div class="col-xs-6">
        <h4>#left-well</h4>
        <div class="well" id="left-well">
          <button class="btn btn-default target" id="target1">#target1</button>
          <button class="btn btn-default target" id="target2">#target2</button>
          <button class="btn btn-default target" id="target3">#target3</button>
        </div>
      </div>
      <div class="col-xs-6">
        <h4>#right-well</h4>
        <div class="well" id="right-well">
          <button class="btn btn-default target" id="target4">#target4</button>
          <button class="btn btn-default target" id="target5">#target5</button>
          <button class="btn btn-default target" id="target6">#target6</button>
        </div>
      </div>
    </div>
  </div>
</body>

However it produces two target5 buttons in the left well. The motive of the challenge seems to be only to copy one target5 into the left well. Is this a bug? And also, egardless of whether it is or isn’t a bug, how would you go about to copying only one #target5 button to the left well?