[alibaba/easyexcel]导出后的excel文件大小为7kb，在wps上打开并且双击任意处后，文件大小变成12kb是什么原因？

 private static void tableWrite(HttpServletResponse response, String fileName, Class mainTableClass,
        List mainTableList, Class childTableClass, List childTableList) throws IOException {
        HorizontalCellStyleStrategy strategy = setCellStyle();
        ExcelWriter excelWriter = null;
        OutputStream outputStream = setResponse(response, fileName);
        try {
            // 写入文件
            excelWriter = EasyExcel.write(outputStream).build();
            WriteSheet writeSheet = EasyExcel.writerSheet(SHEET_NAME).needHead(Boolean.FALSE).build();
            // 指定表头需要使用哪个实例
            WriteTable writeTable0 = EasyExcel.writerTable(TABLE_ONE).head(ImportNoteModel.class).needHead(Boolean.TRUE)
                .registerWriteHandler(strategy).build();
            WriteTable writeTable1 = EasyExcel.writerTable(TABLE_TWO).head(mainTableClass).needHead(Boolean.TRUE)
                .registerWriteHandler(strategy).build();
            WriteTable writeTable2 = EasyExcel.writerTable(TABLE_THREE).head(childTableClass).needHead(Boolean.TRUE)
                .registerWriteHandler(strategy).build();
            List nullList = Lists.newArrayList();
            // 写入-导入须知,仅需要表头，不需要数据
            excelWriter.write(nullList, writeSheet, writeTable0);
            // NC模版要求主表与子表需要空一行
            mainTableList.add(nullList);
            // 写入-主表
            excelWriter.write(mainTableList, writeSheet, writeTable1);
            // 写入-子表
            excelWriter.write(childTableList, writeSheet, writeTable2);
            outputStream.flush();
        } finally {
            if (excelWriter != null) {
                excelWriter.finish();
            }
            outputStream.close();
        }
    }

    /**
     * 设置response
     */
    private static OutputStream setResponse(HttpServletResponse response, String fileName) throws IOException {
        response.setContentType("application/vnd.ms-excel");
        response.setCharacterEncoding("utf-8");
        fileName = URLEncoder.encode(fileName, "UTF-8");
        response.setHeader("Content-disposition", "attachment;filename=" + fileName + ".xls");
        return response.getOutputStream();
    }