Battery draining in new active iPhone 15 128gb

I've just gotten a new iPhone 15 128gb in Vietnam and activated it on Mon (6-Jan 2025). This iPhone was manufactured in Sep 2023 and a brand new one. I notice that for every 4-5 mins of using, the battery drops by 1% (it still has 100% max capacity). Sometimes when I turn off the device and turn back on, I saw the battery dropping by 1% too. Today I set the battery limit at 95% and got charged at 95% @4pm. After using a few time (but not continuously), the battery is now at 83% @8:25pm. I mainly use the iPhone for social media channels, workchat apps, mail and sometimes TikTok.

Is this condition normal for a brand new iPhone ? Please help me. This iPhone is a substitution for the first 15 model I got because of the fault in setting up a new iPhone. The process of substituting a free new phone in Apple Store in Vietnam is super long, unflexible for the customers and really affected my working schedule. I would really want a guidance or answer on this matter before I call the customer service and request another substitution.

I have attached a chart of battery performance (however in Vietnamese but I assume everyone can understand seeing numbers and visuals).