Sorry, but I've never needed to purchase an extended battery. I've always used powerbanks as backup.
The Chinese generic brand battery market is so cut-throat that they are known to fudge the claimed mAh. Unfortunately, the only way to find out is to buy it - try it. Only a Samsung factory branded battery would be more assured to provide quality, and even that is dependent whether it's not a copycat.
I didn't see any extended batteries for the Note 3 on either page of the link you provided.
She said, "Is that a Note 3 in your pocket or are you just excited to see me?"