Without any other context, you generally assume that the target is an accumulator.
So "add 4 coins to that bucket", generally means at the end of that operation the bucket contains at least four coins plus any coins that were already in the bucket.
Huh, I think my brain is not wired to think about `x` as a storage, it is closer to "add 3 to x for x = 2", which then gets reduced to "add 3 to 2" and then the destination is missing...
"Add 4 to x and store result in x" vs "Let x be x + 4"?