Show the maximum scores of the team Boston Red Stockings when the team won in postseason?
SELECT max ( T1.wins )  FROM postseason AS T1 JOIN team AS T2 ON T1.team_id_winner   =   T2.team_id_br WHERE T2.name   =   'Boston Red Stockings'
maximum scores = MAX(wins); team won in postseason refers to wins in the postseason table; team = 'Boston Red Stockings';