S.C. Code Ann. § 56-1-750

In computing the total number of points charged to any person after a particular violation, those accrued as a result of violations which have occurred during the twelve months' period including and immediately preceding the last violation shall be counted at their full value, those accrued from twelve to twenty-four months preceding the last violation shall be counted at one half their established value and those resulting from violations which occurred more than twenty-four months prior to the last violation shall not be counted.