CREATE TABLE "table1_1840433_2" (
  "six_at" text,
  "number_of_editions" real,
  "first_ridden" real,
  "last_ridden" real,
  "most_wins_by" text
);

Question: How many editions have a most wins value of Franco Marvulli (4)?
SQL: SELECT COUNT("number_of_editions") FROM "table1_1840433_2" WHERE "most_wins_by"='Franco Marvulli (4)';