I don't quite understand the meaning of your last sentence. Thank you very much for any advice you can provide.The same user could've been in both. Marketing channels don't (and usually can't) check if they were the first source, but whether a user that completed a goal came through them.
In this case, the same user probably came through both.
If you run campaigns on Google (especially remarketing), it's very important to exclude the audience you gathered from networks you need to compensate for sales.