Lee:
It's more of the unclear wording in the rules.
The end effect of the crit is to reduce your starting shield score.
Its best described by example.
Lets take a Fed Heavy Cruiser with undamaged shields - 24 shield boxes.
during the turn, you take 4 shield hits... dropping you to 20 boxes and one crit that reduces your shields by 5.
This value comes off of the top of the line score of 24, reducing you to 19 shields; wiht a new maximum of 19 boxes.
Then - Let's say you'd taken 7 points prior to this critical, reducing you to 17 shield boxes.
After the critical is applied, you still have 17 shield boxes remaining, but a new maximum of 19.
Meaning that a boost energy roll of 2 will restore you to 19, but anything beyond 2 will count as
boosted shields and go away atthe end of the turn... assuming that you receive no further damage.
Now, lets go back to the beginning. 24 shields and you boost energy to shields and get an average roll of 7 (2D6 at 3.5 each)
This gives you a temporary score of 31.
Take 4 shield hits reducing you to 27 (24 and 3 temporary points) then apply the critical (-5 points).
It's our understanding that you still reduce the starting score, so the new starting score is 19...
This is where it gets "wonky"
the FAQ reads: "if this reduces the starting score below your current score (and you haven’t boosted your shields this turn), then reduce your current Shields to the new maximum."
Our "take" on this is thus:
Reduce your maximum score to 19 (24 starting minus 5 for the critical) and then add back in the 3 temporary points remaining; giving you a score of 22 shield boxes with 19 maximum and three temporary.
Any additional damage will come off of hte 3 temporary first and if no further damage is taken, then you revert to the new maximum of 19 damage at the end of the turn.
We could be wrong, but that's the way we play it.