Mark, the change won't be noticeable immedaitely, likely after a month you'll see things start to get larger (keep in mind the sitemap is to ultimately shove their discovery bot to the side, and tell their crawling bot where exactly to look, so once it gets started it'll work well).
BTW, my rankings are only from 2 months of the sitemap (as I made it, dun dun dun, 2 months ago lol).
