What is the highest number of extra points?
{'header': ['Player', 'Touchdowns', 'Extra points', 'Field goals', 'Points'], 'page_title': '1903 Michigan Wolverines football team', 'page_id': '', 'types': ['text', 'real', 'real', 'real', 'real'], 'id': '1-14342480-15', 'section_title': 'Scoring leaders', 'caption': 'Scoring leaders', 'rows': [['Tom Hammond', '15', '63', '5', '163'], ['Herb Graver', '15', '1', '0', '76'], ['Willie Heston', '14', '0', '0', '70'], ['Joe Curtis', '8', '13', '0', '53'], ['Joe Maddock', '10', '0', '0', '50'], ['Duncan Thompson', '10', '0', '0', '50'], ['Fred Norcross', '9', '0', '0', '45']], 'name': 'table_14342480_15'}