When Denticon hears of this situation, we usually discover that the user is generating a particular patient's unique letter while in the batch letter screen.
When in the batch letter screen, if there are multiple matching records to the batch letter parameter, and the "OK" button is selected, every matching record to the criteria will have a notation in the patient’s Notes screen.
If the desire is to print a single letter for a single patient, Denticon recommend to use the patient's specific listing of reports within the "print reports" option when on the patient record.