I have 14 favorited stories, which I've been keeping sorted by rank. When I added the 14th this morning, every story ranked 11 and above were suddenly ALL ranked as 1. Moving one of the five #1 stories to #2 bumps the current #2 to #1. The net result is that my five top favorites (which are consistently sorted by a pattern I cannot discern) are all equally favorite.
On my actual Favorites page, the numbering is sequential from 1 to 14, with the five #1s appearing in the same order as on the manage favorites page.
Behavior is the same in Safari/iOS and Firefox/Win 10.