I agree with Carribean about the unsourced and POV.  There does exist a number and that number is  962.  This is verified by 
http://sfgate.com/cgi-bin/article.cgi?f=/c/a/2006/05/05/SPGQNIL8UR1.DTL
http://www.pittsburghlive.com/x/pittsburghtrib/sports/s_511371.html
http://findarticles.com/p/articles/mi_qn4179/is_20060507/ai_n16483067
http://www.pittsburghlive.com/x/pittsburghtrib/search/s_458633.html
http://findarticles.com/p/articles/mi_m1571/is_n35_v14/ai_21157150
http://library.thinkquest.org/3427/data/gibson.htm
http://www.blackbaseball.com/players/joshgibson.htm
http://www.coe.ksu.edu/nlbemuseum/history/players/gibsonj.html
http://rhilton4ujournal.spaces.live.com/blog/cns!6AEEB4FD9F1112F8!448.entry
http://www.psacard.com/articles/article4210.chtml
http://mlb.mlb.com/news/article.jsp?ymd=20070802&content;_id=2125626&vkey;=news_mlb&fext;=.jsp&c;_id=mlb
http://www.associatedcontent.com/article/321988/new_homerun_king_josh_gibbons_hidden.html
http://pittsburgh.pirates.mlb.com/news/article.jsp?ymd=20050128&content;_id=936666&vkey;=news_pit&fext;=.jsp&c;_id=pit
http://www.mlb.com/mlb/history/mlb_negro_leagues_profile.jsp?player=gibson_josh
http://www.wvu.edu/~physed/blacksports/jgibson.htm

Notice how many of these are either MLB endorsed articles.  (major league baseball) or blackbaseball articles.  Not articles based off of one book.