If your client replies with C to a reminder message, the appointment will be marked as confirmed in GoReminders. Clients are not forced to reply, so your confirmations will depend on their willingness to do so.
If your client replies with R, the appointment will be marked with a red "!" icon. If your client replies with X, the appointment will be marked with a black "!" icon and greyed out on your GoReminders calendar to indicate it's canceled.
If your customer replies with any other message, you will see their reply on the Messaging tab. If a customer replies to a reminder message, you will receive a text or email if you enable notifications on the Reminder Settings page.
Your customers' confirmations, reschedules, cancellations and replies do not count towards your monthly limits.
Appointments cannot be confirmed with customers replying "yes" to reminders.