What is the largest number of episodes for a 1989 season dvd release? 
{'header': ['DVD Title', 'No. of Discs', 'Year', 'No. of Episodes', 'Region 1', 'Region 2', 'Region 4'], 'page_title': 'All Creatures Great and Small (TV series)', 'section_title': 'DVD releases', 'caption': 'DVD releases', 'rows': [['Series 1', '4', '1978', '13', '14 May 2002', 'N/A', '2 January 2013'], ['Series 1, Volume 1', '3', '1978', '6', 'N/A', '7 April 2003', '1 September 2003'], ['Series 1, Volume 2', '3', '1978', '7', 'N/A', '5 May 2003', '1 September 2003'], ['Series 1 & 2', '8', '1978', '27', 'N/A', 'N/A', '5 October 2010'], ['Series 2', '4', '1978', '14', '15 October 2002', 'N/A', '2 January 2013'], ['Series 2, Volume 1', '3', '1978', '7', 'N/A', '7 July 2003', '5 May 2005'], ['Series 2, Volume 2', '3', '1978', '7', 'N/A', '15 September 2003', '5 May 2005'], ['Series 3', '4', '1979–1980', '14', '16 September 2003', '23 October 2006', '4 May 2006'], ['Series 4', '3', '1988', '10', '14 September 2004', '26 December 2006', '11 April 2007'], ['Series 5', '4', '1988', '12', '19 July 2005', '3 March 2008', '2 April 2008'], ['Series 6', '4', '1989', '12', '25 July 2006', '18 August 2008', '2 April 2009'], ['Series 7', '4', '1990', '13', '14 August 2007', '26 December 2008', '18 May 2010'], ['Christmas Specials', '2', '1983 and 1985', '2', '16 September 2003', '20 October 2008', '2 April 2008']]}