You knew how many appointments dropped out. You did not know why, and that is the only number you can do anything with.
What is new
When you cancel an appointment or set it to no-show, you can pick a reason with it. Which reasons you get depends on what is happening: on a cancellation there are seven, on a no-show three.
Your customer can pick one too, if they cancel themselves through the link in the confirmation email. Then it is there in their words, not in yours.
It stays optional
Deliberately. A required dropdown gets clicked away with the top option, and sixty percent real reasons says more than a hundred percent "other".
Where you see it back
Under Analytics there is a card with the split over the period you are looking at, broken down by who cancelled: you, your customer, or the system during the nightly no-show check.
That card counts on the day the cancellation was made, not on the day the appointment would have taken place. So a cancellation in July for an appointment in August counts in July. That is written under the card's title too, because the other cards on that tab do it the other way round.