CREATE TABLE table_4800 ("Round" FLOAT, "Name" TEXT, "Circuit" TEXT, "Date" TEXT, "Winning driver" TEXT, "Winning car" TEXT)

How many rounds total were there on may 31?
SELECT COUNT("Round") FROM table_4800 WHERE "Date" = 'may 31'
SELECT COUNT("Round") FROM "table_4800" WHERE "Date" = 'may 31'