Ho letto tutti i nuovi messaggi, ma dice che ci sono 21 nuovi posti. Translation: I read all new messages, but says there are 21 new posts.
Alright, makes sense. And thank you. (Sorry for the Italiano I clicked preview and it automatically switched from Inglese to it. Strange..)
Go to view recent post or something like that (that blue link on that screenshot) and you should have a mark as read. Marking as solved.