custom fields code:
add_filter( 'rwmb_meta_boxes', 'your_prefix_register_meta_boxes' );
function your_prefix_register_meta_boxes( $meta_boxes ) {
$meta_boxes[] = array (
'title' => 'User Data',
'id' => 'user-data',
'fields' => array(
array (
'id' => 'user_credits',
'type' => 'number',
'name' => 'Credits',
),
),
'table' => 'prefix_users_data',
'type' => 'user',
'storage_type' => 'custom_table',
);
return $meta_boxes;
}