Why is the modal displayed incorrectly on bootstrap?

Question

Bootstrap

getbootstrap.com/javascript/#modals
I use this example.

<!-- Large modal -->
<button type="button" class="btn btn-primary" data-toggle="modal" data-target=".bs-example-modal-lg">Large modal</button>

<div class="modal fade bs-example-modal-lg" tabindex="-1" role="dialog" aria-labelledby="myLargeModalLabel">
  <div class="modal-dialog modal-lg">
    <div class="modal-content">
      ...
    </div>
  </div>
</div>

<!-- Small modal -->
<button type="button" class="btn btn-primary" data-toggle="modal" data-target=".bs-example-modal-sm">Small modal</button>

<div class="modal fade bs-example-modal-sm" tabindex="-1" role="dialog" aria-labelledby="mySmallModalLabel">
  <div class="modal-dialog modal-sm">
    <div class="modal-content">
      ...
    </div>
  </div>
</div>

Here is the demo. site784.esy.es/ang-test/#/articles