Board Thread:General Discussion/@comment-26082413-20160422181402/@comment-25962175-20160423094434

Highest amount of combined raw damage. This means it's affected by factors such as the ship's FP, the number of times the ship attacked, enemies' armour, and if it was a critical.

If the exact same damage is done then the ship in the higher fleet slot will get it.

Also, during the bombing phase, your individual carriers actually do their individual damage, it's just that it's all done at once so it's impossible to tell who actually did what damage.