On Sept. 17, how many first downs did the oilers have?
CREATE TABLE "schedule" (
  "game" real,
  "date" text,
  "opponent" text,
  "result" text,
  "oilers_points" real,
  "opponents" real,
  "oilers_first_downs" real,
  "record" text,
  "attendance" real
);
SELECT COUNT("oilers_first_downs") FROM "schedule" WHERE "date"='Sept. 17';