It is used on the and of that function (line 107 and 108):
```javascript
 		this.handles.each(function( i ) {
  			$( this ).data( "ui-slider-handle-index", i );
 			$( this ).attr( "aria-valuemin", that._valueMin() ); //here
 			$( this ).attr( "aria-valuemax", that._valueMax() ); //here
  		});
```