Which Overall is the highest one that has a Name of gregory spann, and a Pick # larger than 19?
CREATE TABLE "jacksonville_jaguars_draft_history" (
  "round" real,
  "pick_num" real,
  "overall" real,
  "name" text,
  "position" text,
  "college" text
);
SELECT MAX("overall") FROM "jacksonville_jaguars_draft_history" WHERE "name"='gregory spann' AND "pick_num">19;