Dialplan rule add:

Priority:the value can be ranged from 0-32767. The lower number is the higher priority. Each call will be checked
gradually according to the priority, once the call meets one of the rule, it will stop checking and take the action.


Prefix:
Digit Sequence Syntax:
Elements can be one of the following: Individual keys 0-9.
A subset of keys within brackets (allows ranges): '[' set ']'. (e.g. '4[348] 9' means '439' or '449' or '489')
Numeric ranges are allowed within the brackets: '[digit '-' digit]'. (e.g. '4[2-5]9' means '429' or '439' or '449' or '459')
Ranges can be combined with two more brackets: e.g. '4[347][8-9]' means '438' or '448' or '478' or '439' or '449'or '479.

Leaving it as blank for a special rule, which checks the number of dialed digits.
Once the dialed digits match the prefix, and the phone number arrives at the Max digits,the phone call will take the action.
The digits after the Max digits will be ignored.

Priority Prefix Destination Max digit Action