As a general rule you should dial in your espresso using a scale. The first three shots is normally indicating your espresso flow and the appearance of how well your espresso flow/brew. Your first indicator should be the first drop appearing after activating starting the water flow (pump/bottom) I recommend the first drop to appear approx. at 6-8 sec. in that way your espressoshot will brew as long a 26-31 sec. If it appears before 4 sec. I will recommend you should grind finer and visa versa if the first drop appears to late/after 8 sec or more.
Dosering 20g dobb shot
Ekstraktion 29-31 sek
Vægt i væske 40 g.
Ekstraktion rate  20/40= 0,48%

The dose is calculated using a 20g porta filter Min dose 19g/Max dose 21 g. pr dobb espresso.