After a battery replacement, my iPhone 13 Pro's battery health dropped by 6% in less than 2 months

So October last year, I had to change my previous iPhone due to complications. My Dad had a iPhone 13 Pro from 2021 that hasn't been used since early 2023 (around when the iPhone 15 was launched, if I remembered correctly). The battery before Oct 2023, was at 80%. So we sent the 13 Pro to a third party phone repair shop to get the battery changed (we opted for an ORIGINAL Apple battery) When I got it back it was 100%, as it should be. However, I didn't have the time to transfer and use the 13 Pro just yet. I wanted to so in December I set-up the 13 Pro preparing to start using it. At the end, I had other considerations that made me put the phone aside first.

Come 20th January 2024, I finally had the time to do another factory reset and officially start using the phone. Which I did, all was well until around EARLY Feb I realised the battery health has dropped to 99%. At this point, it didn't really bother me, I thought it was normal judging by my screen time and usage (Clocking an average of 8-10 hours daily, depending) I started to be more cautious of my charging and screen time.

Mid-Feb around 17-18 Feb I checked the phone's battery health and it was down to 97%, which was at that time shocking to me. 20 Feb my phone battery health was 97%, 21 Feb my phone battery health was 96%

I went for a holiday from 22 Feb to 28 Feb where my phone usage DROPPED SIGNIFICANTLY because there was no internet and also cuz I was on a holiday. But in the midst of the trip, the phone battery health managed to drop to 95% and it lasted like this until 3 March 2024.

3 March, I went BACK to the third party repair shop (He's a trusted friend of my Dad's, he was in-charge of a lot of previous phone repairs, so he's not sus or anything) I said I started using this phone and Late Nov last year (which is wrong, cuz I went to check my IG and I posted on 20 Jan this year that I changed my phone again)

He said that everything is normal, just pay more attention to your phone usage. (Average daily screen time still around 9-10 hours, I still don't know how it managed to be so high...when I am hardly on my phone nowadays)

MARCH 6, 2024. 3 days after seeing the guy, my phone battery has officially dropped to 94% (Current Daily Avg. Screen time from 3 March to 6 March is 3h55m)

Is this normal ? What should I do ? (I PAID $200 for this !!! It's $70 MORE expensive than Apple's battery replacement services...) I am worried.