I thought the same but once you open the carton it’s 7 days from the date you open it. At least that was the case with almond milk. I thought they lasted a lot longer especially since they are shelf stable etc. I had a ton of black mold on and around the rim of my almond milk well before the expiration date and that is because I’m fine print it says date of expiration is 7 days after opening.

FYI that’s not a half gallon. Most oat milk cartons are less than 64 oz. The only one I found to be a true half gallon is the walmart GV brand.