All models have a basic rating of 3, with extra stats added accordingly. For Havok you need to count 1 as equaling 0, 2 as equaling 1 and so on. So you come out with (N-1) * modifier.

So, for example, the Karn Trooper has:

1 Speed, 1 Firepower, 1 Close Combat, 1 Psyke, 2 Strength, 2 Armour and 10 Battle Rating. Put this into the above and you get:

1 Strength + 1 Armour + 3 = 10. For instances of -1 you subtract from the total. So the Stats are:

2 = Speed 4 = Firepower 2 = Close Combat 2 = Psyke 3 = Strength 4 = Armour

I have tested these rules for all of them and they work, the only exception is the Glaive Riders where it comes out as totaling 19 rather than 21. I'm trying to work this one out, but feel it may perhaps be a typo as it still works for the other 25 troop types.

As a proof: Banshee (6 Speed, 6 Firepower, 0 Close Combat, 1 Psyke, 3 Strength, 3 Armour and 45 Battle Rating) so (5 Speed + 5 Firepower - 1 Close Combat + 2 Strength + 2 Armour + 3 = 45).

(5*2) + (5*4) + (-1*2) + (2*3) + (2*4) + 3 = 45 10 + 20 - 2 + 6 + 8 + 3 = 45 45 = 45