Double shot is use with ~18-14g of coffee to extract 2oz or ~60ml or 60g over 30secs.

ristretto Is 1:2 ratio isn't extracting 14-18g of coffee to 1oz of liquid? 18g of extraction is ~18ml closer to 1:4 ratio for a double ristretto

Sorry I still clear as mud, the explanation here is extracting for 15secs to yield 30ml of liquid or one shot.
Single ristretto is 15sec to yield 15ml with 14-18g of coffee. Guess it got to do with time and flow rate
http://www.perfectdailygrind.com/2015/06/e...o-vs-ristretto/

Here a ristretto is 7g of coffee to extract 0.75 ounce of liquid.
http://www.gocoffeego.com/professor-peaber...espresso-drinks

Double ristretto is double shot of coffee to yield 1-1.5oz of liquid
http://www.espressocoffeeguide.com/2010/10...-espresso-shot/

On the topic of throwing away espresso and waste. Is ristretto a waste? Throwing our beans that is half extracted?