Hi Ian - thanks for posting and sharing your example! Random numbers are available in rules using expressions. The General Functions in Rule Expressions article documents some of the functions that can be used in expressions including random(0, 10) and pickRandom([10, 20, 30]).
It sounds like what you’re looking for is the ability to perform an action on a random subset of devices. Perhaps the title of the thread could be updated accordingly to ensure the request gets the proper attention it deserves? Otherwise I fear people would interpret ‘Random Number Feature’ to cover the existing expression features mentioned above?
That being said, I suspect that one of the following feature requests could be an alternative way to accomplish issuing actions against a random subset of devices if those requests get enough votes to get implemented: