The Involution part is the process by which God brings the cosmos into existance. The process by which the cosmos and all that it entails raises to
higher states of consciousness is the Evolution part. At least, that is my understanding and interpratation of it.
If Involation were then to equate Probability, that is most likely because the chain of cosmic events -like creates like, this attracts that, cause and effect- are laws that are sound and explored in kind. Evolution equating Possibilty is the reason behind our exploration, if that makes any sense. The possibilties are what we want and wish to do with Evolution; how we want, as a seeker, to tap into it and use it for our developmental ends.