Hey dmc! When the statusCode variable fails to match any of the cases in the switch statement it is caught by the final statement, case let unknownCode:. This is where the value binding happens.
Think of it like this: Lets say statusCode = 419. The switch statement then tries to match 419 to the first 5 of its cases. When it fails to do so, it says “Okay, I don’t know what do with this, but I have this thing called unknownCode and that is a good enough match for me.” Basically saying, in this case let unknownCode = statusCode.