How to apply a sequential number pattern in Pathauto?
You need an additional module for this – Serial Field.


  Unlike Drupal's built-in auto-increment node ID, which is global and
  shared by nodes belonging to all content types, serial fields are
  managed per content type (D6) / entity (D7). For example, the serial
  field of an Invoice instance will generate a unique sequential number
  (starting at 1, then 2, etc.) exclusively for Invoice instances.


You then can use Serial Field + Token + Path Auto - to create serial numbers in urls, for example: http://www.example.com/issue/10 (where 10 is a type scope serial number).