user: Question: Tell me the totla number of goal difference for goals against of 30 and played less than 18
Columns: ['Team', 'Played', 'Draw', 'Lost', 'Goals For', 'Goals Against', 'Goal Difference', 'Points']
Types: ['text', 'real', 'real', 'real', 'real', 'real', 'real', 'real']
Sample row: ['FH', 18.0, 7.0, 1.0, 33.0, 16.0, 17.0, 37.0]
SQL:

assistant: SELECT SUM("Goal Difference") FROM "Table" WHERE "Goals Against" = 30.0 AND "Played" < 18.0;