I've deleted my TripIt subcriptions, but the notifications still stay, so that subscription wasn't related.
I've noticed if I schedule a new reminder, the 15 badge notifications clears and I get 1 notification instead, which is correct. But as soon as I delete that reminder the 15 notifications come right back again. I've deleted my default reminder lists, started new ones, cleared out everything, and the 15 badge notifications still persists. Getting fed up with Apple here.
I also moved the Holidays Subscription Calendar from "My Mac" to iCloud, but it still won't show up at iCloud.com. I'm not sure if that's due to a lack of support for subscription calendars or if there is a bug with this.
I've tried resetting Documents and Data, signing out of all browsers, and clearing caches to no avail. Also deleted the default Calendar and replaced it with a fresh copy. Still no change.