What was the average Jersey # of Steve Griffith, when his Weight (kg) was less than 84?
CREATE TABLE "list_of_united_states_national_ice_hocke" (
  "position" text,
  "jersey_num" real,
  "name" text,
  "height_cm" real,
  "weight_kg" real,
  "birthdate" text,
  "birthplace" text,
  "previous_club_team" text
);
SELECT AVG("jersey_num") FROM "list_of_united_states_national_ice_hocke" WHERE "name"='steve griffith' AND "weight_kg"<84;