ICA means in-character actions.
ICC means in-character consequences.
So ICA=ICC means that in-character actions have in-character consequences.
What does this really mean? For people who have this set as a roleplaying? preference, it means that while the game is consent-based, they prefer to play in such a manner where in-character actions bring about real consequences and that they will generally consent to going where the roleplay takes them.
Does this mean that they have relinquished their right to call on the consent rules? No. But it means that they probably won't call on those rules very often.
Sometimes staff call for ICA=ICC because repeated warnings to a player that their continued course of action will bring about hefty consequences has been either ignored or waved.
ICA=ICC doesn't always call for bad things to happen to a character, but quite often does. Some players embrace this, however, looking forward to where ICC takes their characters.