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

        if( tableAnnotation.numberedRows() || hasCustomerHeader ) {
            ApiUtil.isTrue( !hasCustomerHeader || dataTable.hasHorizontalHeader(),
                "Using numberedRowsHeader in @Table without having a horizontal header." );

            int rowCount = dataTable.getRowCount();
            List<String> column = Lists.newArrayListWithExpectedSize( rowCount );
            addHeader( customHeader, column, dataTable.hasHorizontalHeader() );
            addNumbers( rowCount, column );
            dataTable.addColumn( 0, column );
        }
    }
The default implementation to format a table argument
jgiven-core/src/main/java/com/tngtech/jgiven/format/table/DefaultTableFormatter.java