I want the total number of gross tonnage when entered service was 1903
CREATE TABLE "ships_of_the_great_eastern_railway" (
  "ship_s_name" text,
  "entered_service" text,
  "ended_service" text,
  "gross_tonnage" real,
  "type_of_vessel" text
);
SELECT COUNT("gross_tonnage") FROM "ships_of_the_great_eastern_railway" WHERE "entered_service"='1903';