How does Volatility work?

Hi,
can someone tell me which damage variable gets scaled by this gem? Is it base weapon damage, all weapon damage, active gem % damage mod, summarised overall damage spread, some partial damage variable?

Ryslatha's Coil specifies "Physical attack damage", this gem doesn't, so it should apply to all attack damage (Physical/Elemental/Chaos).

It looks like it just gives you higher highs and lower lows, thus a wider spread of attack damage by the supported skill.

Lets say i have weapon that
Deals 7-62 base damage, added 1-100 lightning dmg,
using Cobra Lash gem that
Deals (75-125.4)% of Base Attack Damage and
(3-113) to (5-169) Added Chaos Damage.

Which of these min-max values gets scaled by Volatility?