Talk:Damage calculation

When a Card says "During Damage Calculation only" does the destruction of the monster continue?I made an Alien Deck, and I placed the field Spell "Otherworld- the "A" Zone", I attacked my friend' Izanami that was in Defense mode (1800)with "Alien Skull" (1600) according to A-zone, my friends Izanami would have a DEF of 1500, killing it. however he stated that that "During Damage Calculation only" meant only damage was changed, so Izanami would not be destroyed, but I wouldn't take the 200 LP damage I usually would. I think he is wrong though

could someone clear up the meaning? cuz otherwise I can't use Alien's against him because the whole point of "A" counters is to weaken your opponent's monsters enough to be able to destroy them among other things.