CREATE TABLE "mixed_martial_arts_record" (
  "res" text,
  "record" text,
  "opponent" text,
  "method" text,
  "event" text,
  "round" real,
  "time" text,
  "location" text
);

Question: What is the number of rounds that took place for the fight that lasted 6:21?
SQL: SELECT COUNT("round") FROM "mixed_martial_arts_record" WHERE "time"='6:21';