Unless otherwise approved by the National Regulator, when the value of the quantity indicated by any continuously indicating digital or semi-digital indicator is increasing, the change to the next higher figure in any decade higher than the units decade must occur when the indication in the units decade is moving between its highest figured graduation and zero or is moving the last one tenth of its travel towards zero, whichever is the lesser, and the change in the higher decades must be completed when the indication in the units decade has reached zero and conversely when the value of the quantity indicated is decreasing, the change to the next lower figure must occur when the indication in the units decade is moving between zero and its highest figure graduation or for the first one tenth of its travel from zero and the change in the higher decades must be completed when the indication in the units decade has reached the highest figured graduation or has moved one tenth of its travel.