i want to rotate values for annotations in google charts because it overlapped as shown in image:

then i need code to rotate the annotation values. the code used is: "columns" => array(

                "month_db" => array("label" => "Months"),
                "Retail_Budget" => array(
                    "type" => "number",
                    "label" => "Budget",
                    "prefix" => "",
                    "annotation" => function($row) {
                        return "" . milion($row["Retail_Budget"]);
                    }
                ),

ok, how can i solve overlapping??