If it doesn’t have the While parameter it is not a while loop, it is a standard event.
In GDevelop every single standard event is repeatedly executed multiple (60-30) times a second top to bottom similar to an If statement. Think of the events editor as a main loop that constantly repeating and you can add If statements (standard events) and also While and For loops (special events) inside this main loop. Not sure if it helps to get the picture.
I did not watch the tutorial and I don’t have time to do it maybe someone else will. From what I see it has no purpose unless the value of NextLevel <= 0 at some point in the game.
Did you complete the tutorial and the game? Maybe it is going to be important or fixed in a later chapter.
Just do what he does and maybe add a comment to remember the purpose of that part is unclear. Once you have completed the tutorial and it is still unclear, post the question below the video as he maybe not active on the forum.
Anyway, unfortunately I can’t help you with this one, maybe someone else will.
Good luck.