G'Day Sue, Open to interpretation, however with espresso the time for extraction is always around 30 seconds, less time = under and more time = over extraction. As far as the double goes, many people use a double/triple basket - 14 to 18 grams and grind for an extraction of 30ml in 30 seconds, others will go for 60ml in 30 seconds, I'm in this camp, some will even use a triple basket with over 20 grams of coffee. Remember water flowing through ground coffee for no more than 30 seconds. 🙂