Battery Drain when turned off?

I turned off my phone at 17%, waited 30min than turned it back on, battery is at 8%.

Revliss How many charge/discharge cycles does the battery have? Was the temperature significantly low where the device was off?

Has it been a long time since its fully charged to 100%?

Was the phone warm while off?

Does the phone battery drain quickly while turned on?

Did it remain at 8% for a minute after booting up? A high load will lower voltage and battery remaining estimation.

Allowing the battery to repeatedly reach 0% or remain at 100% for days/weeks can cause jumps in battery % like this.

I woke up this morning (after posting this) and I had a GrapheneOS notification about the battery saver.

The phone was not charged for a couple of weeks. Battery does drain quickly.