Replacement Battery Losing mAh Fast

I installed a new Battery into my iPhone 6 about a week ago. Now, usually this wouldn't bother me, but the battery reading software when I first installed it said it had 1750 of 1810. Which is not much of a difference but still a fluctuation for a battery. Now, 14 cycles later it is reporting that it can only handle 1650 of 1810. And I will unplug the phone and plug it back in and it maybe will go to around 1670 and sometimes lower to around 1610. Is this normal to see in a battery for fluctuations in capacity? Or should I order the warranty replacement?

It was a company off of amazon, probably not the best quality battery.

https://www.amazon.com/gp/product/B0769H...

Recently I replaced the iPhone 6s Plus battery, but ordered the parts from iFixit, and it has a maximum capacity of 2865 of what it should only have 2750 mAh.