That gives the knees of a seated adult room to fit under the worktop, so the stool can be pulled in close enough to eat. We would not go below 25 cm, and that only for short meals; with less than that, most people sit sideways.
The table shows what each overhang depth allows. The deeper end of the range makes long meals more comfortable and suits taller people; the shallower end suits islands used mainly for breakfast and coffee.

















