What are the least losses of Warrnambool with more than 6 wins and less than 630 against?
CREATE TABLE "1940_ladder" (
  "club" text,
  "wins" real,
  "losses" real,
  "draws" real,
  "against" real
);
SELECT MIN("losses") FROM "1940_ladder" WHERE "against"<630 AND "club"='warrnambool' AND "wins">6;