There's a bug with the damage prediction if you use Endiswall or Binlor to max out your physical resistances using Stone Skin. (EDIT: Forgot to mention, for this issue to occur your character needs to already have a fair amount of physical resists, so it's mostly going to happen with the monk or the paladin)
To reproduce (this is just the fastest way to do this):
1. Start a run in the Venture Cave as a Monk with Binlor Prepped
2. Worship Binlor and get enough Piety for Stone Skin
3. Find a level 2 monster (or any monster whose hits you can stack twice if you have max Stone Skin for the first hit)
4. Look at the damage prediction (for the Hero's health) for the first two hits; you'll note that the damage prediction for the second (and further) hit is off
5. Attack the monster once
Results: After the first hit, the damage prediction will be corrected to its proper value; the original prediction had the hero taking too much damage.
Here are screenshots:
1. I have max Stone Skin and am looking at the level 2 Goat. The damage I'm supposed to take on the second hit is slightly off...
2. I just hit the level 2 goat and the damage prediction has corrected itself.
3. And here's the two cropped together for easy comparison: