It means your lymphatic system is drinking up the castor oil. Your system is probably thirsty for it. Sometimes I need a big amount, sometimes quite little.
I usually do salt water flushes when I want a flush to go quick. (and olive oil flushes)
I always suggest choline (phosphatidlycholine) in the form of lecithin, egg yolk flushes, phosphatidylcholine, or coffee enemas to help build up bile reserves when I hear folk are trying to do liver flushes. Choline is the base element for bile, and it's been the biggest help to me!