add_filter('frm_after_display_content', 'add_view_total_to_after_content', 30, 4);
function add_view_total_to_after_content($after_content, $display, $show, $atts){
    if ( $display->ID == 145 ) {
        $entries = $atts['entry_ids'];
        $total = 0;
        foreach($entries as $entry){
            $current_value = FrmProEntriesController::get_field_value_shortcode(array( 'field_id' => 6, 'entry' => $entry ) );
            if ( $current_value ) {
                $total += $current_value;
            }
        }
        $after_content = str_replace('[sum_6]', $total, $after_content);
    }
    return $after_content;
}