The notification simple said '1', reports Engadget.
I personally got it on a Samsung Galaxy S8+ and a Galaxy A50S, and for both devices, clicking it did nothing. At least nothing that I could see: It didn't fire up the application and offer any explanation of what it could mean.
According to Yonhap, Samsung issued a statement revealing that the notification was an internal test gone wrong.
Samsung Electronics announced in a Samsung Members announcement that "This is a message sent wrong during the internal test, there is no effect on the customer's smartphone" and "I'm sorry for the inconvenience."