Q: Meaning of [Ref] in parameter decelaration

Accidentally I saw this event declaration of FMX.TLIstView.ItemClickEx:

procedure TForm1.ListView1ItemClickEx(const Sender: TObject; ItemIndex: Integer;

  const [Ref] LocalClickPos: TPointF; const ItemObject: TListItemDrawable);

I have never seen the addition of [Ref]. Where is it documented? I guess it means "by reference", but was is then the difference with just declaring LocalClickPos: TPointF?

(Using Delphi DX10)