well each ship only has its own, so its 13 each individually. and each subunit (aux/sf) as its own individual
so 1 PBC has 13 AP (your Starvipers and Droids have their own to operate once you've deployed them)
it could move forward 2 spaces at the cost of 3AP each, 13-6 = 7. So now it spends those remainint 7AP to fire 7 weapon emplacements, 2 of its 2 Quad TUrbolasers and 5 of its 8 Lasers canons is 7 emplacements.
So using your 13AP in this hypothetical turn that one PBC moved forward 2 spaces and fired 7 weapons at whatever targets
AP is the 'activity fuel' controlling the volume of what a unit can do in a single turn.
Note for your PBC to fire all of its weapons, (10 total emplacements) in one turn, it has to spend 10AP, leaving only 3AP remaining.
Because the PBC is a Heavy class ship, to move 1 space costs it 3AP. While a smaller ship moves at less AP cost.
So adds tactical depth more or less instead of just saying "everything can be done once in a turn always" I guess. In the previous model, the PBC would be much more limited actually in terms of movement, because with 13 AP, it can move 4 Grid Spaces forward (costs 12AP) in a single turn. In traditional methods of regulating what and how much of it can be done, a PBC would never be able to move that far in a single turn, it's speed would be a 1 or a 2 max.
I think it's positive across the board and simplifies everything once you adapt your thinking to it
So in your turn you move all your individual units and take other actions with them according to their AP and try to use up as much of your AP as you can because it doesn't carry over, it just starts full again for each unit come your next turn. So if you have 1AP left at the end of the turn for a capship after doing everything else you wanted to do with it, you probably want to just use it to do Damage Control action as in the Action List.