I don't see the map but I'll assume there's 1 interior wall and 1 physical barrier between the orcs and the grenade.

End of the turn, it explodes. Starting damage is 18p.

First the blast meets the Physical Barrier spell with 5+5+5 resist pool (5 structure 5 armor and +5 from frag grenade's AP which is actually positive rather than negative). Roll, 5 damage down, 13 to go. The barrier sustains more damage than it has structure and winks out, the mage gets it 2 sustain dice back.

The interior wall, 1+2+5. The orcs are lucky, another 3 damage down and 10 to go. The wall turns into wood chips and glue.

Blast weakens as it travels 1 meter, 9 damage.

These orcs weren't born yesterday and wear armor vests, they have 6+5=11 armor, which is more than grenade's 9 so it turns from physical to stun. 5 body + 11 armor = 16 resist pool, one takes 4 stun the other 5, both manage to stay on their feet.

The blast gets to exterior walls with 10+21 resist pool, shreds the wallpaper and doesnt do any structural damage (21 armor > 9 damage, turns to stun, wall doesnt care)

The blast is absorbed, because naturally we not crazy enough to play with chunky salsa rules and we want this combat to end somewhere before 4am.

next turn.

I knew it was too easy

Specifically 2nd edition

That's grimdark, not cyberpunk though