Hooking up ACF repeater fields to the shema.

repeater-meta.php

//acf stats repeater
array (
			'key' => 'field_5a27ee3a83076',
			'label' => 'Stats',
			'name' => 'stats',
			'type' => 'repeater',
			'instructions' => '',
			'required' => 0,
			'conditional_logic' => 0,
			'wrapper' => array (
				'width' => '',
				'class' => '',
				'id' => '',
			),
			'collapsed' => '',
			'min' => 0,
			'max' => 0,
			'layout' => 'table',
			'button_label' => '',
			'sub_fields' => array (
				array (
					'key' => 'field_5a27ee4683077',
					'label' => 'Label',
					'name' => 'label',
					'type' => 'text',
					'instructions' => '',
					'required' => 0,
					'conditional_logic' => 0,
					'wrapper' => array (
						'width' => '',
						'class' => '',
						'id' => '',
					),
					'default_value' => '',
					'placeholder' => '',
					'prepend' => '',
					'append' => '',
					'maxlength' => '',
				),
				array (
					'key' => 'field_5a27ee4c83078',
					'label' => 'Value',
					'name' => 'value',
					'type' => 'text',
					'instructions' => '',
					'required' => 0,
					'conditional_logic' => 0,
					'wrapper' => array (
						'width' => '',
						'class' => '',
						'id' => '',
					),
					'default_value' => '',
					'placeholder' => '',
					'prepend' => '',
					'append' => '',
					'maxlength' => '',
				),
			),
		),

//make sure to use ObjectType
use GraphQL\Type\Definition\ObjectType;
use GraphQL\Type\Definition\Type;

// stats repeater

add_action('graphql_stats_fields', function($fields) {

        $statsType = new ObjectType([
        'name' => 'Stat',
        'description' => __( 'The description of your process type', 'your-textdomain' ),
        'fields' => [
             'project__Label' => [
                              'type' => WPGraphQL\Types::string(),
                        ],
                        'projects__value' => [
                              'type' => WPGraphQL\Types::string(),
                        ]
        ]
        ]);
        $fields[ 'stats' ] = [
        'type' => Type::listOf($statsType),
        'description' => __( 'Your processes repeater field in GraphQL', 'your-textdomain' ),
        'resolve' => function( \WP_Post $post ) {
            $fp_metabox_process_group = get_post_meta( $post->ID, 'fp_metabox_process_group', true );
            return ! empty( $fp_metabox_process_group ) ? $fp_metabox_process_group : null;
        },
        ];
        return $fields;
},99 );