TL;DR: Tighten the burrs to (safe) maximum and then loosen by rotating the cogwheel by 1⅓ rotation (8 tooth). Using this as a starting point should give you grind size resulting in 2m30s brew time (30s preinfusion, 1m30s pouring water, 30s finish).
I own Hario Skerton hand coffee grinder for about 16 months now. With Skerton, after a dozen or so grinds, you usually get a part of coffee bean stuck between the burrs which requires you to take the grinder apart and clean it.
If you don’t clean it, it will result in your grind size becoming more and more inconsistent. This is a hassle for pour over coffee brewing and something that I’ve been trying to improve ever since I got this grinder.
In the beginning I’ve been struggling with how to set it back to my preferred grind size after cleaning. Skerton does not have any kind of grind size indicator which made me rely on my intuition and on visually estimating the distance between the burr parts. This has been prone to errors and I usually got it right only after 2–3 adjustments.
Since then I’ve developed a better way to set it up after the cleaning:
First, tighten the burrs to (safe) maximum. Make sure not to damage the burrs!
Then, loosen the burrs by rotating the cogwheel by 1⅓ rotation (8 tooth).
And lastly, put everything back together.