(Answered) SCA Adjusting Fire; Page 102

[JugernautJedi]

Can you elaborate on what the last sentence means.

“The successive shots fired modifier can only apply once per turn, though it is cumulative over multiple turns.”

Particularly the “cumulative over multiple turns” part.

[nckestrel]

If two artillery units fire at the same target this turn, the first gets no modifier and the second gets a -2.
If the same artillery units fire at the same target the next turn, assuming they go in the same order, the first gets a -2, and the second gets a -4.

If you have three artillery units and they fire at the same target, the third is treated the same as the second.  The first gets no modifier, the second and third both get -2.
Next turn, the first gets -2, and the second and third get -4.