Coffee can hold twice its weight in water, so whatever the amount is put into the portafilter, the water should be double that dosage. So, for example, if I were to put 10 grams of grounds into the portafilter, the amount of liquid that gets weighed out at the end inside the espresso cup should be 20 grams. If you have access to a scale, you should weigh out the amount of espresso grounds before putting it into the machine.