Well, the combat modifier means that there's a 30% bonus to both offense and defense... however, I never really sat down and saw if it works that way in game (mainly because by the time I got Events Predictor, all my defense fleets had already reached Elite->Legendary, as well as the individual ships, as well as having ECM, Stealth, and Scattering armour on them, so figure about 140% defense, what's an extra 30% going to mean?