The pay of a substitute teacher shall not be less than eighty percent of the daily rate of the state basic salary paid to teachers: Provided, That any substitute teacher who teaches in excess of ten consecutive instructional days in the same position shall, thereafter, not be paid less than eighty percent of the daily rate of the state advanced salary based upon teaching experience: Provided, however, That any substitute teacher who teaches in excess of thirty days in the same position shall be paid the daily rate of the advanced salary, within that teacher's county.