You should scale up if you'd like to experience a more challenging version of that movement, and you should scale down if the current movement is a little too challenging at the moment.
A movement should be scaled up if you are able to keep up with Tyler or go faster. If you are not completely out of breath and feel you could easily complete more reps of that movement, it is probably time to scale up!
A movement should be scaled down if you are unable to keep up with Tyler in the interval (or round) or you are completely out of breath for the next movement. This means it would be worth trying to scale this movement down for the time being until you're ready to see a more challenging variation later.
And remember, you can always scale a movement back up or down if you find the scaled version too challenging or not challenging enough, so don't hesitate to test the waters to get your workouts feeling just right for you!