Nine should be the maximum number of tick marks between numbers.
Additional Information:
Major and minor graduations should be used if there are up to four graduations between numerals. Major, intermediate, and minor graduations should be used if there are five or more graduations between numerals. The use of these graduations on a conventional meter face is shown in Figure 1.9. Table 1.2 shows graduation dimensions as a function of viewing distance for a conventional meter face.
Table 1.2 Index heights for various viewing distances.
Figure 1.9 Graduation dimensions for 3-foot viewing distance.