SELECT COUNT("Opponents") FROM table_20981 WHERE "Record" = '6-4'
How many opponents were there for the game recorded as 6-4 in the Atlanta Falcons 1978 season?
CREATE TABLE table_20981 (
    "Game" real,
    "Date" text,
    "Opponent" text,
    "Result" text,
    "Falcons points" real,
    "Opponents" real,
    "Record" text,
    "Attendance" real
)