Yeah you're reading it right!
You have to place subsequent templates so that they also maximise hits on the first formations. The rules for extra templates read
Quote:
Extra Barrage Templates: Large barrages may receive extra Barrage templates. The Barrage table will tell you if a
barrage receives any extra Barrage templates. Place any extra templates so that they touch the first template that
was placed, and so that no templates overlap. All units under the templates are attacked with the barrage’s to hit
values. Note that once the first template has been placed, the attacker may choose where to place the additional
templates, as long as they are touching the first template, and no line of fire, placement or range restrictions apply
(see below).
My blue text
The see below text is "using barrage templates" in which we can read
Quote:
In addition, templates must be placed in such a way as to
get as many enemy units from the target formation under them as possible within the restrictions for lines of fire and
range. This stops players ‘sniping’ at important units with artillery.
But it also says that you can place it over several formations so basically if you can maximise on the target formation and also hit other formations then you're good to go! So the first formation can't be ignored:)