user: Question: What is the smallest average for beijing guo'an when they played more than 240 games?
Columns: ['Season', 'Total Attendance', 'Games', 'Average', 'High avg.', 'Team', 'No. Of Clubs']
Types: ['real', 'real', 'real', 'real', 'real', 'text', 'real']
Sample row: [1994.0, 2155000.0, 132.0, 16326.0, 40000.0, 'Sichuan Quanxing', 12.0]
SQL:

assistant: SELECT MIN("Average") FROM "Table" WHERE "Team" = 'beijing guo''an' AND "Games" > 240.0;