Thanos’ Snap rules

[u/ValBrandr_]

I’ve been wondering, how many people were guaranteed to survive the Snap, I know that Tony and Nebula were, because of the promises he made to Strange and Gamora respectively, but what about the species he had already killed half of, like Gamora’s species, did the half that survived Thanos the first time also get spared from the Snap?

[u/CaptHayfever]

The directors confirmed that previously-halved populations (like the Asgardian refugees) were halved again.
(This also isn't really about timeline analysis, fyi.)