"You can change the crawl rate (the time used by Googlebot to crawl the site) for sites that are at the root level—for example,
www.example.com and
http://subdomain.example.com. You can't change the crawl rate for sites that are not at the root level—for example,
www.example.com/folder.
Note: Crawl rate refers to the speed of Googlebot's requests during the crawl process. It doesn't have any effect on how often we crawl or how deeply we crawl your URL structure."