<p>
  <label for="amount">Текущее положение:</label>
  <input type="text" id="amount" readonly style="border:0; color:#f6931f; font-weight:bold;">
</p>
 
<div id="slider"></div>

  var isChanged = false;
  $( function() {
    $( "#slider" ).slider({
      animate: "fast",
      value:6,
      min: 1,
      max: 11,
      step: 1,
      slide: function( event, ui ) {
        $( "#amount" ).val( Math.round(ui.value / 2) );
      }
    });
    //$( "#amount" ).val( $( "#slider" ).slider( "value" ) );
    $( "#slider" ).on( "mousedown", function( event, ui ) {
    	if (!isChanged){
			
           // var value = Math.round( $( this ).slider( "value") / 2);
            //alert(value);
            //$( this ).slider( "option", "step", 6 );
            $( this ).slider( "option", "step", 2 );
            //$( this ).slider( "value", 3 );
            isChanged = true;
        }
    } );
  } );