Hi,
Small healing potion tooltip value is 30. Fane had 63 Health.
So he drank one potion, his Health went down to 35.
You say healing potion. Seems to me you are forgetting an important thing here. Fane is undead, he take damage from normal healing potions that you use on living characters, like a human, or a dwarf. Undead heal when they drink poison, or are hit with spells, grenades, arrows, or anything else that deal poison damage.
