My lo's dream feed usually lasted about 5-15min and he took anywhere from 2-8oz (sorry, I don't know mL). It seemed like he would make up for the day. If he drank a lot that day his DF would be small. If he didn't drink much, then his DF would be big. I would usually offer him a bottle that had the same amount that I put in his other bottles.
Hope that helps.
Kimberly