GForm limit

function calculateTodayReservedSeats() {
    var msg = "We're sorry, the event is full.";
    var ss = SpreadsheetApp.openById('1W3YYzxCnefXsdY3lV99q7Pm3KWWt7Ef-Oiq9mG9oM9k');
    var sheet = ss.getSheetByName('Responses');
    var lastRow = sheet.getLastRow();
    var person1 = sheet.getRange(2, 3, lastRow - 1, 1).getValues();
    var person2 = sheet.getRange(2, 4, lastRow - 1, 1).getValues();
    var i, count;
    for (i = 0; i < person1.length; i++) {
        count += person1[i][0];
        count += person2[i][0];
    }

    if (count > 60) {
      form.setAcceptingResponses(false).setCustomClosedFormMessage(msg);
    }
}