They had 10,000 in August because they had 30,016 visitors with all 3 months combined so if they had 10,005 visitors in June and 10,011 visitors in July you add 10,005 + 10,011 which is 20,016 and to find the visitors in August you subtract 30,016 - 20,016 which gives you 10,000 so they had 10,000 visitors in August
