New M1 MacBook Air Battery Lasts 8 Hours only (one day old MacBook)

Hi, I purchased this MacBook Air 2020 from Apple Store on April of 26th 2021, when I started it first time' it said the last charge was on 4 April 2021(maybe when they packaged it in box) now it was charge for about 80% I use my laptop for eight hours and my battery was down to 7% I only used safari, watched an hour YouTube video and 100 minutes movie on VLC, replied some texts etc, Brightness was mid tier 7 nits, It was supposed to last 12 hours minimum, my second charge to 83% with the same use gave me only 7.5 hours till it came down to 8% requiring a charge.

In the 8.5 hours, I'm not counting the time I didn't use my MacBook and the lid was closed, which is about I guess 12 hours commutative.

I still have 10 days to return and ask for a refund or replacement, I need some suggestions.

Thanks