Every state I've ever hunted in has possession limit as twice the daily limit (after the second day of hunting). As said, "possession means possession" that you've taken and still have in your possession while hunting, at home in the freezer, etc. If you shot 8 ducks, which for instance MN duck possession limit is this year after the first 2 days, you couldn't shoot any more until you ate some of the others.
Don't think that Game Wardens won't check or call and have another Warden go to you home and check to see if you have a freeze of game birds either if they have reason to believe you have more than you possession limit. In other words, don't give them any reason to believe that you have more than daily or possession limits if spoken to. That goes for fishing too. They are very talented at asking questions about how you've done before when they stop to check licenses, etc. You may say, "we got our limits last weekend." He says, "so you had a big fish fry, duck banquet..." or whatever. If you say no and you have more animals in you possession, he knows he's going to be calling a Warden in your area to come to look in your freezer. And they will. I've not been in that situation. But I've had them quiz me about past success and whether we eat what we got before.