Interesting - this new Ascaso stainless steel i-Mini has an external appearance that looks somewhat like the Le Lit PL53. The Le Lit is a grinder that a lot of folks on H-B love, has "innards" that are essentially identical to the "old" Ascaso i-Mini, has a "boxy" stainless steel exterior unlike the "old" i-Mini's more rounded cast aluminum exterior and instead much like this more boxy "new" stainless steel Ascaso i-Mini, and I think was a US-only import. (If you search, you'll find many references to the Le Lit, e.g...
Visit here ) However, this new Ascaso seems to have a larger conical burr than either the old i-Mini or the Le Lit.
As for how to judge the proper grind... with the i-Mini and my Gaggia Factory lever machine, here's what I did (not that what I did is necessaily correct...) I started by turning the i-Mini's fine/course knob far into the "fine" range ("many, many, many" turns clockwise - "many, many, many" being, of course, a very precise technical term of art...

) Basically, I wanted to get it to the point where the burrs were just touching and the grinder wouldn't grind - essentially to get the grinder to the "finest" "end of the line". Then I dialed the knob back a few turns toward "course" so that it would actually grind - and dosed into the pf. I tamped lightly and gave it a try in the Gaggia Factory. The Gaggia Factory essentially choked, so I knew I had the i-Mini still set too fine. After a few more turns of the i-Mini's knob back toward "course", I tried again... Eventually, through several iterations of trial and error, adjusting both the i-Mini's grind knob and my tamping, I arrived at what seemed to be the optimum grind knob setting and tamping parameters for the "resistance in the pull" that I wanted. BTW, this grind knob setting was still relatively close to the "fine" end of the line. Of course with each different variety/batch of beans - and even with each successive day as the same batch of beans ages - the grind knob setting and amount of tamping needs to be slightly ajusted for optimum results - generally a bit more fine (and tamped a bit harder) each day as the batch ages... All this "dialing in" remains a mix of trial & error and intuition... it always seems like the next try will be the one that will nail it just right... but the illusive nature of the process is part of the fun!
Hope this helps...