CREATE TABLE table_21623 ("Series #" FLOAT, "Season #" FLOAT, "Title" TEXT, "Directed by" TEXT, "Written by" TEXT, "Original air date" TEXT)

What was the number of seasons that was directed by Joanna Kerns?
SELECT COUNT("Season #") FROM table_21623 WHERE "Directed by" = 'Joanna Kerns'
SELECT COUNT("Season #") FROM "table_21623" WHERE "Directed by" = 'Joanna Kerns'