Update - 12.16pm: Fianna Fáil's Education Spokesperson, Thomas Byrne, has revealed that he knows of a second Leaving Cert adding error from this year's exams.
Mr Byrne told Today with Sean O'Rourke show on RTE Radio 1 this morning that the mistake was discovered at the start of September.
He said: "I am aware of another adding error where the figure was totted up and put on the front of the answer book, where there was a mistake made between the front of the answer paper and the actual Leaving Cert exam sheet.
"Now, as I understand it, in that case, the State Examinations Commission treated it as an administrative error and changed the exam sheet almost immediately, certainly within a day.
"And I don't know why this particular situation couldn't have been treated similarly, I mean Rebecca Carter, she is a fantastic lady for doing this, but there may be other cases similar to hers out there that didn't go to the High Court."
Mr Byrne also outlined his concern over the response of the State Examinations Commission to the judgement in Ms Carter's case.
He said: "They haven't actually said that they accept the decision and they will give her the marks. They have left open the question of an appeal."
A careers guidance teacher, Brian Mooney, said: "All they are doing is they are saying they have committed now, that her paper will be re-examined and re-corrected by a completely new examiner and that person will give her a grade according to that person's mark.
"The presumption is that he will give her as much as she already got, will correct that adding mistake and that result will end up as her getting that extra mark.
There are calls for third-level institutions to extend their course registration cut-off dates.
It comes after a 19-year-old won her case against the State Examinations Commission over its appeals process.
Rebecca Carter was unable to start her chosen course three weeks ago because of a totting up error on one of her exams.
A High Court Judge yesterday ordered the SEC to determine her appeal by this Friday instead of mid-October, to allow her to start college next week.
Former President of the Institute of Guidance Counsellors, Betty McLoughlin, said universities and colleges need to allow time for the process to be completed.
Ms McLoughlin said: "The simplest thing, in my opinion, that would have to move would be that the third-level system would wait, would not close off the entrants into their courses until the process has taken place.
"Because I do know the absolute focus when they are doing this process has to be correcting every single error that might have happened through the process of the correcting."