How is damage assigned when multiple units are in a Showdown?

In a showdown, damage is not assigned unit-to-unit. Instead, each player sums the total Might of all their living units at the battlefield and independently decides how to distribute that total damage among their opponent's units.

According to Rule 460.2.c:

The Assignment Sequence

1. Totaling Might: You add up the total Might of all living units you control at that battlefield.
2. Assignment: Starting with the Attacker, each player assigns their total damage to the opponent's units.
   • Note: The attacker assigns all their damage first, then the defender assigns all their damage.
3. Simultaneous Dealing: Once both players have finished assigning their damage, all assigned damage is dealt simultaneously to the target units.

Key Rules for Assignment

• Lethal Damage: Units must have lethal damage (damage equaling or exceeding their Might) assigned to them in full before any damage can be assigned to a different unit. You cannot "spread out" damage if a unit has not yet been assigned lethal damage (Rule 460.2.c.3).
• Mandatory Requirements: You must obey any abilities that dictate how damage is assigned. For example, if an opponent's unit has Tank ("I must be assigned combat damage first"), you must assign lethal damage to it before assigning damage to other units (Rule 460.2.c.5).
• Over-assigning: You cannot assign more damage to a unit than the minimum required to make it lethal, unless you have no other eligible units remaining to assign damage to (Rule 460.2.c.4).
• Existing Damage: If a unit already has damage marked on it from previous effects (like spells), that damage counts toward the total required to reach "lethal" status during the assignment step (RiftJudge FAQ #871).

This is my interpretation based on Rule 460.2 and related FAQs. No official FAQ exists that contradicts this interpretation.