Half Damage

[Typhon]

Yhea it's a basic and I remember seeing the answer/example SOMEWHERE just can't find it now.
Figured it'd be in with Attacks or Advanced Damage but no luck.
Anyway, what I'm wondering is:
COMBAT INSTINCTS
You react instinctively to fresh opportunities.
Benefit: Once per round when an adjacent opponent attacks
you and misses, you gain a free attack against him. If this attack
hits, it inflicts only 1/2 damage (rounded up).

there. It's in a couple other places too but wondering half of what?
Half of the damage rolled, rounding up? Then add any weapon/stat modifiers or is it half of the sum total damage (rolled number, stat bonuses, everything) and half that? Or is it any damage done to the target (thus total damage and then after DR applied)? A couple of spots have clairifications added to the "1/2 damage" note (like Last Stand). Most of the other 1/2 damage would imply 1/2 the total dealt (roll, mods, etc) but before any defensive reductions. Like spells and breath weapon reflex saves for half would be half of the total amount being done by the attacker but before DR/Resists.

[Mister Andersen]

You hit, you calculate your damage outputjust as you would any other hit, halve it, apply it, target applies their DR and resistances.

[Typhon]

ah bummer! Was hoping for a half on the roll then add bonuses since my finesse does almost as much as my max damage with the weapon.