iFixit Battery Replacement Indicates 92% Health after calibration

Hey everyone!

I have just yesterday replaced my old MBP battery with one of the iFixit batteries that comes with the replacement kit. Now I saw very bad performance right out the box, it gave me about the same battery life as before (2hrs). So I googled and found out that I'd have to calibrate the battery.

I followed this guide https://www.lifewire.com/calibrate-macbo...

Before doing the calibration, the health of the battery was at 100% and current capacity at around 8.6k mAh which was even more than the "design capacity" of 8.460. And at the step where I was supposed to drain the battery, it lasted forever! I watched Netflix and youtube on loop at 3-4 bars away from max brightness for about 4h30m! I was super happy, and was looking forward to waht kind of time I'd be able to get once the calibration was complete.

After doing the calibration I am seeing an improvement from 2hrs to 3hrs... So I somehow went from 4h30mins on almost max brightness during the calibration process to 3hrs predicted on very low brightness (I was in my bedroom at maybe 4bars of brightness).

The battery health went down to 92% and the current capacity is at about 7750 - 7850, it keeps changing, going up and down sometimes.

What gives? Was the battery shipped to me faulty? Shouldn't I have done the calibration? Should I do it again? Maybe with a less demanding scenario? I have read in this guide https://www.newertech.com/batteries/powe... that one should do a more reasonable approach and just drain the battery more slowly and steadily as to ensure maximum battery calibration correctness.

I'm on a MBP 15" Early 2013 with all the latest updates installed.

This is what I installed, https://eustore.ifixit.com/en/Parts/MacB...

However, mine didn't have the plastic arm in the middle shown in this picture of the kit.

https://ibb.co/eOqQoo

Not sure if that is important or not, just thought it might be worth mentioning...

Ok, so after using it a bit more, and then leaving it closed for a while and now opening it again it indicates 100% health and correct current charge... It shouldn't fluctuate so much, right?

So, both coconut and my won monitorer say the same now. As I said, for some reason it changed...

And why would I have to replace the battery, again, I just replaced it yesterday.

So the Full Charge Capacity keeps going down slowly...

Is that normal? Sorry to ask so many questions, this just seems irregular to me.

Here is the screenshot, as you can see only Firefox, and it has a low impact. Also, the remaining time has normalized in a way. It's only the Maximum Capacity thing which is weird atm.

I don't get it... After using it till about 20% I left it to charge without using it and left the charger on a while longer and now this is the capacity...

After using it again for a bit, I am again seeing weird battery life. I have currently 3h33m left with 78% battery. As before the only app using power is Firefox, I am on 1 bar of brightness and am not watching video...

And even if I was, just a few hours earlier I saw the same time left being displayed, but while watching videos and on halfway to full brightness...

Oh and once again, the full capacity has changed dramatically to a whopping 8.7k mHa...

I genuenly hope that this isn't the battery being faulty as it was really hard getting the old one out...