Rule of 4 & 2

I have recently discovered the rule of 4 & 2, but i'm slightly confused, one perception is to multiply outs by 4 on the flop and 2 on the turn and that's it. The other perception is to multiply outs by 2 on the flop if NOT going all in, or by 4 on the flop if going all in, and again by 2 on the turn.. I have seen reference to both versions more than once but both give different results, I was wondering what variation is the correct one?

Only use the rule of 4 if you're guaranteed to see the turn and river.

So, on the flop, if villain shoves and it's only you to call or fold, if you call, you are guaranteed to see the next 2 cards because there is no more betting possible.

If seeing the river isn't guaranteed (because you can still fold the turn), you do the rule of 2 I'm the flop-to-turn. And again on turn-to-river.

Simple way to remember:
-Rule of 4 = Guaranteed turn and river.
-Rule of 2 = turn and river is not guaranteed.

Rule of 4 is very rarely used.

Thank you, your explanation made the penny drop, very much appreciated.

there is the same rule 20 that on this issue also indicates that it is necessary to pay attention to the opponent's stack, and it will not be accurate to get information about the right decision on the basis of only outs, the pot odds and the position also affect the decision on what to do on each street.:captain: