State 0 is normally quiescent, so that the entry for the zero state with eight zero neighbors should be zero. Zero states do not age, but there is a period of transition in which a cell that has just recovered still has the apparent age at which the recovery took place. That is because the counter in planes 1, 2, and 3 is reset by a zero in plane 0, or incremented by a 1. But the reset cannot take place until the cell has actually become zero, which is one generation later.
Otherwise the lines describing aged zero cells would be meaningless; to adhere strictly to the Zhabotinsky model, all such lines should be filled with zeroes. But they can also be used for other purposes if one wishes to think that a cell just recovered may relapse, starting to age anew, according to the condition of its neighbors.