The PortionPro Rx controls portions by distributing equal amounts of food at preset times in preset amounts by volume based on how you program the feeder. The daily totals vary from ½ cup all the way up to 6 cups. From ½ cup up until 3 cups the amount changes in 1/8 cup increments. From 3 cups to 6 cups the amount changes in ¼ cup increments. For cats you can program either 2, 4, or 6 meals per day; where 2 and 4 are custom times you set and 6 meals is automatically divided up over a 24 hour period (which is most natural and healthy for cats). Dogs are offered either 2 or 3 meals per day and both of those options are completely customizable times. Cats naturally eat frequent small meals a day, the PortionProRx feeder has the ability to feed 6 small a day which healthier for cats. Free feeding cats is unhealthy for cats.