including letters, digits and special characters is recommended for better security.
The password has to be more than 9 characters/digits and has to fulfill at least 3 options among 4 options
below:
1) Numeric (0-9)
2) Capital letters (A-Z)
3) Lower case (a-z)
4) Special characters (!, @, #, $, %, ^, &, *, (, ), etc)
Figure 16 : Change Password on first boot