$('#example').select2({
  data: [
     {id: 'test1', text: 'January', subText: "Test1"},
      {id: 'test2', text: 'February', subText: "Test2"},
     {id: 'test3', text: 'March', subText: "Test3"}      
    ],
    placeholder: 'Select a month',
    escapeMarkup: function (markup) {
     return markup;
    },
    templateResult: function (d) {
     return '<span>'+d.text+'</span><span class="pull-right subtext">'+d.subText+'</span>';
    },
    templateSelection: function (d) {
     return d.text + ' ( ' + d.subText + ')';
    }
}).val('test2').trigger('change');

.pull-right {
  float: right!important;
}

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<link href="https://rawgit.com/select2/select2/master/dist/css/select2.min.css" rel="stylesheet"/>
<script src="https://rawgit.com/select2/select2/master/dist/js/select2.js"></script>

<select id="example" multiple="multiple" style="width: 300px"></select>