CREATE TABLE table_29337 ("No. in series" FLOAT, "No. in season" FLOAT, "Title" TEXT, "Directed by" TEXT, "Written by" TEXT, "Original air date" TEXT, "Production code" TEXT, "U.S. viewers  ( million ) " TEXT)

What is the total number of production code listings of episodes written by Matthew Lau?
SELECT COUNT("Production code") FROM table_29337 WHERE "Written by" = 'Matthew Lau'
SELECT COUNT("Production code") FROM "table_29337" WHERE "Written by" = 'Matthew Lau'