The concussion protocols involve answering some recall questions and then comparing them to their pre test scores.
They also need to satisfy / answer a lot of questions about how they are feeling physically, eg. headaches, ability to sleep, irritability, etc. A lot is based on how they feel, so Reed telling
@emjaycee he feels fine is a good start.
From what I can gather Matto was satisfying all the recall tests but then close to the game was indicating that some of those physical signs were occurring which is why he was getting named earlier in the week and then getting pulled closer to the game.
Here you go...Take the recall part of the test (some of those first general questions are altered to be specific about the footy game they are playing, eg opponents, venue, who scored last, etc:
And a bit more reading of what happens immediately:
https://www.abc.net.au/news/2017-04...concussion-test-works-in-rugby-league/8441808