Brand new Honor 400's battery drained by 10% just leaving it off overnight.

As per title, I just bought the phone and unpacked it last night. The starting battery was around 33-35%, I didn't charge it before using.

After an hour of two of using, the battery fell by 10%, then after I turn off the screen and left it for the night, 8 hours later, I woke up and see the battery level dropped to 11%, which is another 10% or so drain.

The phone is using MagicOS9, AI function turns off, as far as I know.

Is this normal, or is this because I didn't charge it to full before I started using it?

Thank you all in advance.