Grey Knights- cleansing flame

[Vlad]

Hello, fellow BoLSers!

Could you aid me in interpretation of that psychic power's wording?
How should we roll for wounding? Cast spell, do one roll of 4-6 and every enemy model suffer or you roll 4+ for each model?

[Hellstorm]

roll a d6 for each model. on a 4+ they take a wound.

[Exterminatus]

Group 1 assults group 2, now maxamise base to base contact and move everyone into the assult. step 2, make a psychic, if passed add up the total of enemy models in the assult, ALL of them even if there are more than just the 2 groups. Roll that many dice, on a 4+ that many models take a wound. resolve the cleasning flame and remove dead models. Now do your attacks.

"To the righteous we bring hope. To the tainted we bring fire."

- Castellan Garran Crowe