Time to get visa

We are going on a cruise in April, making multiple entrys (three), and arriving in Hong Cong several days early. We are able to go to Los Angeles to apply for an express tourist L, but wont leave for the trip until April. We read about each stop being for two months, which would be good for six months. Does that start when we make our first entry or when we get it approved. In other words if we get one in December will it be good for the first entry in April. Thank you.
Harvey