CREATE TABLE table_16751596_13 (lead_maragin VARCHAR, dates_administered VARCHAR)

On July 17, 2008, what was the total number of lead maragin?
SELECT COUNT(lead_maragin) FROM table_16751596_13 WHERE dates_administered = "July 17, 2008"
SELECT COUNT("lead_maragin") FROM "table_16751596_13" WHERE "July 17, 2008" = "dates_administered"