Variable is not in scope(from official tutorial vid)

Hello folks!

I’m going through the [Massive UE4 Tutorial Playlist][1] and currently watching [10 - Using Loops : Procedural Level Design][2] video. I’m exactly following all the steps and having a trouble with “Variable is not in scope”. And so far it looks like a bug.
Here’s my BP:

Even with ‘make vector’

And, btw, there’s a dude with the same problem in the comments below the video:

I’m a bit familiar with the C++ programming process, but I have no idea how a variable declared as a global one could be out of scope - this is nonsense for me.