Can someone help explain what N0 means, and how to calculate it?

I see the formula is N0= variance ÷ (EV×EV)

What exactly do i use for my EV numbers?

I just want to know how many hands it would take to get to the "long run" in a blackjack game where the variance is known and the game pay back is 100.1% flat betting.

Im a bit confused as to what to input as my EV numbers, and should it be calculated as 4×N0 to be considered the "long run"?

Im trying to look up info on my own but am kind of stumped.