CREATE TABLE "departmental_service" (
  "number" text,
  "previous_br_no" real,
  "taken_into_deptal_stock" real,
  "withdrawn" real,
  "disposal" text
);

Question: Name the most previous br number
SQL: SELECT MAX("previous_br_no") FROM "departmental_service";

Question: Name the total number of previous br number for number 21
SQL: SELECT COUNT("previous_br_no") FROM "departmental_service" WHERE "number"='21';