Volcano mechanics

Don't quite understand how the blasted thing works.
A unit can walk straight through a torrent of rocks and get 0 damage.
A unit can be hit by a single rock and get full damage.

Can someone explain me, what volcano object data fields are responsible for and how to configure them properly?

Building damage factor - 2.00 (default) - it means buildings take double (2x) damage from rocks

Data - Rock Ring Count - 3 - how much rocks every wave

Wave Count - 8 - how many waves

Wave Interval - 5.00 - time between every wave

So normal volcano should shoot 24 rocks in 40 seconds.

Area of Effect probably means how long rocks fall away from volcano. Duration is stun length.