phone battery replacement specs don't match the original- is it safe?

@roborachel, that can be an issue in some cases; for example I have a drill that runs on Ni-Cd (nickel cadmium) batteries. I'd love to convert it to lithium ion, which would work fine for the drill, but the problem comes in when you try to charge it. A Ni-Cd charger will not put out the correct charge curve or voltage for a Li-Ion battery.

Cell phone batteries are a different story, The thing is, each and every cell phone, and most laptops for that matter, use a custom-designed battery. In general, a battery that's made for one phone won't go into another due to either the physical size and shape of the battery or the connector being different, not to mention any charge, voltage or temperature sensors built into the battery.

So for cell phones you won't find a battery that says it's made for your phone that's incompatible; in fact, just the opposite is true - if it doesn't say it's made for your phone, you can assume it won't work.

So if someone is selling a battery for a Samsung Galaxy J3 Prime, then it's basically always safe to assume it's compatible. It's actually fairly rare for a replacement battery to have different specifications than the original, but that's not always the case as you found out. In your case the new battery you got doesn't hold quite as much charge as your old one did; about 15% less than the original.

It won't hurt anything; the battery itself will work fine, but you'll end up having to charge it a little bit more frequently than you did with the original battery.

On the other side of the spectrum are batteries being sold as some sort of 'gold standard' that are supposed to hold amazingly more charge; unfortunately those claims never hold up under scrutiny; just ask @oldturkey03 about that; he's written papers on the subject after testing those supposed high capacity batteries and found that their claims aren't true.

The upshot to all this is, while I'd have been a little miffed at getting a battery with less capacity than it did when I took it in - and you would have a reasonable complaint with them if it bothers you - the battery they gave you should work fine for your phone for the life of the battery.