Extraction knowledge of Espresso Elite rule: sweet spot formula

Al Critzer's understanding of Espresso extraction has become the most common concept of Espresso in Europe and the United States. The translation is as follows: starting with the result that 30cc/ 30sec gets a perfect Espresso. These two values of course depend on beans, and the differences in baking method, baking degree and formula ratio will naturally lead to changes in the reference point. The extraction quantity and extraction time are mutually related.