Source

File: wp-includes/sitemaps.php

function wp_sitemaps_get_max_urls( $object_type ) {
	/**
	 * Filters the maximum number of URLs displayed on a sitemap.
	 *
	 * @since 5.5.0
	 *
	 * @param int    $max_urls    The maximum number of URLs included in a sitemap. Default 2000.
	 * @param string $object_type Object type for sitemap to be filtered (e.g. 'post', 'term', 'user').
	 */
	return apply_filters( 'wp_sitemaps_max_urls', 2000, $object_type );
}