Because cranking the screen resolution up uses more battery and that is what the phone is estimating what will happen but may not be accurate due to real world usage.
Current Phone > Samsung Z Fold³ 5G. > Software : Android 12 ~ Samsung One Ui 4.
Yes, yes thank you, I know that, but it's ridiculous that it estimates only 4-5 minutes less of the battery time. It's ridiculous.