And this is precisely why it's insane and counterproductive to have unread counts on an RSS feed.
Don't obsess over reading every last article. It's a feed. Read what looks interesting. Let other things go. Don't track what you've read or what you've missed. There's nothing down that path but frustration and stress.
And yet, almost no RSS developers see the wisdom in this, and they prefer to embrace the dumb idea with open arms.