LMSC Sure, there may be overlap of % at 400Kruve (I can’t say what proportion of that % would be fines), but “one full mark” isn’t a unit of anything, just a fairly random interval, from grinder to grinder. Looking at what happens at the other end of the distribution will show a bigger difference (but this will be different from one grinder to the next).
I went from 67.5 to 68.5 (so a change of nearly 2%) on my Zero and saw a 1 cup brew and a notable change in taste with the Aromaboy. My Feldgrind is at 28 at an equivalent setting, so one full mark will have a bigger impact with that grinder (4% per mark), my Timemore Nano might be at 17, or 18 (5-6% per mark)?
Dry bed time doesn’t have the resolution to dial in for best taste, only to show a catastrophic error in grind setting.
