private static void addNumberedColumns( Table tableAnnotation, DataTable dataTable ) {
        String customHeader = tableAnnotation.numberedColumnsHeader();
        boolean hasCustomerHeader = !customHeader.equals( AnnotationUtil.ABSENT );

        if( tableAnnotation.numberedColumns() || hasCustomerHeader ) {
            ApiUtil.isTrue( !hasCustomerHeader || dataTable.hasVerticalHeader(),
                "Using numberedColumnsHeader in @Table without having a vertical header." );

            int columnCount = dataTable.getColumnCount();
            List<String> row = Lists.newArrayListWithExpectedSize( columnCount );
            addHeader( customHeader, row, dataTable.hasVerticalHeader() );
            addNumbers( columnCount, row );
            dataTable.addRow( 0, row );
        }
    }
The default implementation to format a table argument
jgiven-core/src/main/java/com/tngtech/jgiven/format/table/DefaultTableFormatter.java