Is where a kitchen starts to feel cramped
The total walk between sink, hob and fridge. Under that with two people in the room and you are queueing.
Is the gangway an island needs
Clear, on every side being used. It is the number that decides whether your room can have one, and most rooms cannot.
Centimetres, and worth changing
The standard height suits a 5ft 8in cook. If the person who cooks most is not, it costs nothing to change now and cannot be changed later.