That is only for dining where you give them a credit card number to hold the reservation. There are only a few places that do that. Most of them are free to make, change, or cancel as many times as you want. You can change any of them, but the reservations where you have given a credit card (castle and Norway) you have the 48 hours to cancel without penalty.
If you were had a Crystal Palace (Pooh and friends) reservation, and the day before your DD panicked at a character greeting, you could cancel at anytime and not be penalized… Most are this way.
That being said, people can make reservations as much as 180 days out, and they can be very hard to get at the last minute. I would suggest making them, and then canceling as needed… It is better to have the reservation than not, and try to get one.
If you have the dining plan, I would highly recommend getting reservations ahead of time. Good luck!