user: Question: When Semi Final (2nd leg) is the round what is the highest attendance?
Columns: ['Date', 'Round', 'Opponent', 'Result', 'Venue', 'Scorers', 'Attendance', 'Match Report']
Types: ['text', 'text', 'text', 'text', 'text', 'text', 'real', 'text']
Sample row: ['20 September 2005', 'Second Round', 'Bournemouth', '1–0', 'Home', "Roberts 86'", 3346.0, 'Report']
SQL:

assistant: SELECT MAX("Attendance") FROM "Table" WHERE "Round" = 'Semi Final (2nd leg)';