SELECT MIN("Attendance") FROM table_63875 WHERE "Opponent" = 'perth glory' AND "Round" = '9'
Which Attendance has an Opponent of perth glory, and a Round of 9?
CREATE TABLE table_63875 (
    "Round" text,
    "Date" text,
    "Opponent" text,
    "Score AUFC \u2013 Away" text,
    "Attendance" real,
    "Weekday" text
)