Partially returned Orders

SELECT order_number
     , ordered_date
     , ordLines
     , returnLines  
  FROM (SELECT /*+ cardinality (oeH 1) */
               oeH.order_number
             , oeh.Ordered_date
             , count(distinct oeL.line_id)   ordLines
             , count(distinct oeLR.line_id)  returnLines
          FROM apps.oe_order_headers_all oeH
             , apps.oe_order_lines_all   oeL
             , apps.oe_order_lines_all   oeLR
         WHERE oeH.ordered_date BETWEEN SYSDATE - 50
                                    AND SYSDATE - 49.75
           AND oeH.header_id = oeL.header_id
           AND oeL.line_id   = oeLR.reference_line_id (+)
         GROUP BY oeH.order_number
                , ordered_date
        HAVING COUNT(*) > 1
       ) a
  WHERE ordLines    > returnLines
    AND returnLines > 0;