You really need to weigh both the grinds you put in the pf, and the shot afterwards.
I always weigh the grinds going into the pf, and go for 17-18g in the portafilter, and about 35g shot in 25sec.
One thing to remember when dialing in the grinder, is that there is a good amount of grinds from the previous grind in the chute, making the next grind a mix of the two.
Always remember to tilt the grinder forward and bang it on the sides to get everything out.
I usually grind about 14g, then tilt it for the last 3-5g, and then using around 17g in the portafilter.
It is also har