Assuming that all calls will be passing through a Scenario before distribution, you may use the built in random function
Inputs an integer parameter and returns a random integer in the configured range (i.e., 0 to one less than whatever number is defined as “max”). This function can be used to launch a random percentage of surveys.
=random(100) will return integers between 0 and 99 (i.e., a total of 100 integers)
For an example of how to use this function, see section Scenario Building Exercises.
If variable < 6 - route to A
If variable >6 and <10 - route to B
The routing described above could be a request skill/service, followed by a Find Agent, or alternatively a route out of Bright Pattern via a Connect call block.