Question about attack skills damage ("% of base" versus "%")

What is the difference between "X% of Base" and "%" ?

Using Ice Strike as example:

"

Attack Damage: (65–203)% of base

Third Strike
Attack Damage: (145–452)%

The first part of the description i understand it is relative to the weapon. Is the second part relative to the base skill damage ?

Example (ignoring conversions):
Attack Damage: 75% of Base , Third Strike Attack Damage: 150%, Weapon : 100 phys

First two strikes would deal 75 (0.75 * 100) and the thrid would deal 112.5 (1.5 * 75) ?

Now to Herald of Ice:

"

Explosion
Attack Damage: (70–286)%

What is the base value to calculate the damage here ?

There's no diffrence, it's a poe2db thing.