The Engine is not able to process two functions simultaneously. One function will always happen before the other. I reached out to some of our developers to find out how the Engine determines which function to call first, and it sounds like there is no official definition for how this is handled. It may be based on creation order, but you may not want to rely on that always being the case.
If the functions in question are not related in anyway, and don’t care about what the other one is doing, then you most likely won’t have any problems. However, if you need to make sure that one function always happens before the other if they are called “simultaneously,” then you will want to include a check to ensure the second function is delayed briefly if it was called first. Using a very brief delay or timer will allow the other function to be run first.