CREATE TABLE table_64912 ("Rank" FLOAT, "Lane" FLOAT, "Name" TEXT, "Nationality" TEXT, "Time" FLOAT)

What's the lowest rank of the United States with a time less than 24.63?
SELECT MIN("Rank") FROM table_64912 WHERE "Nationality" = 'united states' AND "Time" < '24.63'
SELECT MIN("Rank") FROM "table_64912" WHERE "Nationality" = 'united states' AND "Time" < '24.63'