S.C. Code § 7-13-1140
If more ballots shall be found on opening the box or if more ballots, which are tabulated by vote recorder equipment, or if the number of votes tabulated on voting machines in any polling place exceeds the number of voters listed on the poll list at such polling place, the vote total for each candidate or issue shall be reduced by that fraction of the excess vote cast that his total vote bears to the total number of votes cast in the polling place. Fractional parts of single votes shall be disregarded.
If the number of votes cast by any type ballot or on machines in any polling place exceeds the number listed on the polling list by ten percent or more, the county executive committee or the county board of voter registration and elections, as the case may be, shall order a new primary or election at the polling place concerned if the outcome of the election could be affected. Only those who signed the poll list shall be permitted to vote in any such new primary or election.
S.C. Code § 7-13-1140