Thanks for your purchase from Zerolemon.
The phone and the charger of Note 4 are programmed as fast charge function and the battery percentage is also programmed to show the percentage of one battery.
But actually, the note 4 10000mAh battery is Tri-cell battery.
For example, when the phone shows the battery at 10% but it is not like that actually.
The 10% percentage you see is based on one battery capacity(3333mAh), so the battery capacity you still have is 3333*2+3333*10%=6900mAh charge.
Then you use 6900mah divides 10000mah, then 69% comes out. Which is approximate to 65 % as you described. So at this point, you can use at least 2 days with a "10%" charge.
As the battery is over-sized, the only accurate method to test this battery capacity is based on how much time you can use from 100% to 0%.
If you have more concerns about our product, just feel free to contact us.