Inconsistency between Amethyst & Bismuth/Elemental flasks?

Amethysts increases your resistance by a % of your maximum resistance. Bismuth (& Ruby/Sapphire/Topaz) increases your resistance by a % of your current resistance (or possibly a lower %). They are both worded the same way with out any indication that they work differently.

For example:

Fire resistance: 40%
Cold resistance: 39%
Lightning resistance: 43%
Chaos resistance: 18%

After I use an Amethyst (+35% to Chaos Resistance) & Bismuth flask (+35% to all Elemental Resistances)

Fire resistance: 54%
Cold resistance: 53%
Lightning resistance: 57%
Chaos resistance: 53%

The Amethysts works as expected but the Bismuth appears to increase my resistances by 14% (approximately 35% of their current amount)

Anyone know why this is?

Thank you, didn't realize that Annihilating Light acted upon flasks.