Usually a pretty noticable amount, like a couple mm, but I make small bottles (2 oz). I was short on bottles and put 4oz in one, and I noticed last night how much cream was in that one. Like 3/4" or more. It was a ton of cream.
My milk has always seemed really creamy to me, but LO was a preemie and has always been on the small side so my body probably makes fattier milk for his needs. He seems chunky to me, but he is actually on the normal/thin side for babies his age I think.