i think what they mean is that the amount of enums are a variable.
therefore the range should match the number of enums.
not sure if a for each node exist for enums or not, but if it does that could be a way. Or if you can put them into an array then use a random node.
edit: looks like there is a for each loop for enums
ForEach over Enums - Programming & Scripting / C++ - Epic Developer Community Forums (unrealengine.com)
so you can use a random bool to break out of the loop with an enum. But that leaves a case where none were selected you have to handle. There’s a few ways you could do it but won’t be too hard.