Can Singularity deal 6 damage to the same unit twice (12 total), or can it deal 6 damage to just one unit?

Ruling: "Up to two" means you can choose zero, one, or two units. Singularity deals 6 damage to each chosen unit. You can deal 6 to just one unit, but you cannot deal 12 damage to the same unit.

Nuances:

• You can choose to deal 6 damage to one unit and skip the second target entirely
• You cannot target the same unit twice to deal 12 damage