The coffee quantity dial controls how much coffee is ground into your filter. The single and double filters come with an indication level that, once tamped with the smart tamp station, the ground coffee level should reach. This indicates the perfect amount of ground coffee for brewing. If you change the type of coffee beans or over time you may need to slightly adjust the dial, but typically once it is set it will remain consistent. This dial also controls the "pre ground coffee" function that bypasses the automatic grinder.