Right;
A single pulse by a single PPD will create only one volley.
In SFB, this may be a volley of 5 (1+3+1), but you'd resolve the 3, then one of the 1's, then the other 1.
This is due to them coming in from different shields, and possibly being able to damage different phasers as a result.
e.g. You hit a Hydran cruiser with down shields. This ship has 2xFA+L Ph-2's, 2xFA+R Ph-2's, and a LS and RS Gat. on You hit his #3 shield - so he takes 3 in the #3, 1 in the #2, and 1 in the #4.
You resolve the 3 through the #3 first. The FA+R phasers and the RS gat can be killed here.
Then you resolve either the lone internal through the #2 or #4 (I _think_ it's owner choice, but it may be random which one is taken first - doesn't matter). Let's say we do the #2 next.
If a phaser is hit, it can be scored on the FA+L, FA+R or the RS gat.
Then you resolve the lone internal through the #4. Only the RS gat and LS gat can be scored on a phaser hit.
But even though you (in SFB) have to concern yourself with the ORDER that you take the internals, they're all considered the same volley.