user: Question: How many instances is the unlocked N/A?
Columns: ['Circuit', 'Difficulty', 'Turns', 'Direction', 'Setting', 'Conditions', 'Unlock Order', 'Unlocks', 'Unlocked by']
Types: ['text', 'text', 'real', 'text', 'text', 'text', 'real', 'text', 'text']
Sample row: ['Athens', 'Medium', 11.0, 'Clockwise', 'Day', 'Dry', 2.0, 'Berlin', 'Rome or Fiorano']
SQL:

assistant: SELECT COUNT("Setting") FROM "Table" WHERE "Unlocked by" = 'N/A';