Example custom display

example.php

<?php
$ui[ 'fields' ][ 'manage' ][ 'my_custom_field' ] = array(
    'label' => 'My Custom Field',
    'custom_display' => 'my_custom_field_pods_value'
);

function my_custom_field_pods_value( $row, $obj, $value, $field, $attributes ) {
    $value = $row[ 'a_number_field' ] + $row[ 'another_number_field' ];
    
    return $value;
}