I’m currently at about 15, for this particuilar bean, brewing espresso. It varies a bit as the beans get a bit older, but not hugely. I do find a SMALL tweak makes a big difference. The only use I really have for the numbers is that I record what I did for every short as a learning tool. The first thing it taught me was that about a quarter, from say 14 to 14.25, is a pretty big jump.
The next thing it taught me was that consistent tamping is important. Due to shoulder pain, I find tamping quite hard and consistent tamping harder still. But worth taking my time to do, because even a little lighter on the tamp makes a big difference to my shot time. I’m wondering, given my shoulder prblem, if I should have just gone for a Puqpress. The cost, though …. ouch.
Anyway, back to grind setting - another lesson I learned quickly is to not to try to relate what suits MY grinder, calibration, bean choice and espresso machine probably bears no resemblance at all to what someone else gets. As other have said, go by the coffee. I’m still trying to maintain consistency in as many factors as ossible, so using the same beans (well, different roasts obviously, but the same choice from the same supplier), in a 20g VST with a target 19.1 in, 38-ish out, in 30 sec +/- about 4 or 5 sec. But even 40 sec is drinkable. Keeping everything else the same, I end up tweaking grind settings about 0.1 or 0.2 of a Niche number at a time, if I get two or three on the trot outside my target output.
Next for me? Try adjust the “in” a bit and study the effect. i.e. what about 18 in, or 20 in? Or what about 2.5:1 ratio? In other words, just trying to learn what to do …. by trying what turns out to be what not (shudder) to do.
I am finding a few extra avenues of the rabbithole I was warned home espresso turns into.
Still, it’s all part of the fun …. I tell myself. :D