No need for the third roll there. No variable target numbers or anything.
It's just 2x the 13d6 to determine the hits from each short burst. So, 7 hits on the first and 8 hits on the second.
By the way, DAAAAAAAMN.
7P base +1P ammo +7P net hits +2P autofire = 17P
Soak roll 8d6.hits(5) → [6,1,1,6,5,4,2,4] = (3) 14P = 3 more dead
and 18P
Soak roll
7d6.hits(5) → [1,3,4,3,2,4,6] = (1) = 17P = 4 more dead.
Mischief splits up. There's.. only 5 of them left.
2 stay on Jack
8d6.hits(5) → [3,6,3,2,5,1,2,6] = (3)
8d6.hits(5) → [1,3,4,3,5,6,2,1] = (2)
3 attack Gardener
9d6.hits(5) → [2,5,2,3,1,4,4,2,6] = (2)
9d6.hits(5) → [3,1,6,5,3,1,3,3,3] = (2)
9d6.hits(5) → [3,3,5,4,5,5,3,4,3] = (3)
Since these things are knee-high at best, I count your legs as unarmed if you want to use your unarmed skill for blocking.
Remember to include the cumulative -1 penalty per defense.