rulefused ..ahm.. confused by rules

[hdmgurps]

Hi to all..

First, I´m not sure wether this upcoming question is well posted in this thread. However as it concerns my own S&S fantasy style game I shall try here.
Second, it concerns a (houseruled) spell from the imaginative mind of Enraged Eggplant (probalbly well known around the community:

"Chain Lightning"
From this link:https://enragedeggplant.blogspot.com...ng-spells.html

Not being a native speaker nor rules-god I am confused how the second (and following) attacks work!?

Let´s assume the follwoing situation. i am attacked by three enemies. The first 1 yard away, the second 4 yards away and the third 7 yards away from me.
I have a innate attack skill of 15. I succesfully cast the spell and throw it unto my 1st target rolling a 10. (assume targets do not use a successful defense). --> I would hit target #1.. and then..??

I do not get how the following attack calculation would function/be calculated.

Sorry for my stupidity.. any help, pls.

(PS.. pls feel free to move this thread to the appropriate forum if necessary)

Thx from Germany