Possibly not normal. Keep an eye on it. If it continues dropping rapidly like this, there's most likely something wrong.
In iOS 17.0.3, there's a toggle to limit the charge to 80%, which WILL increase the lifespan of your device. This is important for devices of this caliber. I would enable it if I could on my iPhone 13 Mini. Lithium batteries are under higher strain when full.
However, if you've owned your device for a while, it's possible that Apple's software is finally giving you the actual percentage without bias towards 100%. It's still strange for the most part, so keep an eye on it!
Additionally, if your phone is new, i.e., less than 3 months old, then there is a 100 percent chance that there is an issue, and you should consider getting it checked at the Genius Bar or an Apple repair center. Such checks are provided for free within the one-year warranty period or Apple Care. Though still wait to see if it gets worse.
As with all defects, they get worse with time. So you will know when there is something wrong! Don't worry.