I just got Klingon Armada and I am looking forward to playing but I have a sticking point in the rules where I don't understand shields.  Would any kind soul here consider helping enlighten me?

The Admiralty rule is:
"In order to score damage, a hit must penetrate
the target's shields. For each hit scored as a
result of the to-hit roll, roll a number of dice
equal to the weapon's IMP. For example, if a
weapon with an IMP value of 2 scored two hits,
a total of four impact dice would be rolled.
Compare the result of each die separately to
the target's shield rating; each die that exceeds
this value causes a point of impact to
the target."

Looking at, say, a Federation CA Heavy Cruiser, shields are in two areas:

One large set of boxes: 15, 14, 12, 11, 9, 8, 6, 5, 3, 2
Six shield facets: { 3, 2, 1} and some {2, 1}

The sum of the shield facets equals the sum of the larger shield box.

My question is how exactly is "shield rating" determined here?   Since each die is resolved independantly it makes no sense to roll against a 15 on an undamaged ship.  One would never hit!   So it seems as if I need to roll against the facet rating --keeping in mind Klingon Armada also makes one roll a 1-3 on d6 to see if it hits that facet or another one.

What confuses me is the large box (15..2) and what to do with it. 

It seems like I should be able to ignore that box and do the following:

- If there is a hit roll impact dice (die) to see if it is higher than the shield rating for the facet in line of site.
- If it is higher roll a d6 to see if damage is done to that facet or another one chosen.
- If there are none left then ignore it.  The shield has served it's purpose and soaked up a bunch of damage (though it seems odd to me that the roll is ignored; the SFB player in me wants to see the unshielded ship get hit harder).

Can anyone clear this up for me?  I am not following the rules here and the example didn't help.