I wouldn’t keep tightening based on the dry bed time. The dwell time between last water in and dry bed naturally varies by bean, it doesn’t indicate extraction, nor remedial changes by itself. 10 marks on a Niche Zero isn’t the kind of range that is ‘tweaking’ for brewed, it’s more like the kind of change you’d use for a different brewer, or a very large change in brew size.
For 330ml water the average dwell time was 26 seconds, but from 10-45.
For 186ml water the average dwell time was 25 seconds, but from 16-43.
All my best brews on the Aromaboy have been in a 5-6 mark range, on the Niche Zero, for a given brew size.
I’d be more driven by changes in the cup. Flat/muddy/silty mouthfeel go coarser. Tangy/unripe/weak go finer.