I found online a cheat sheet stating the following rule for Multiple Enemies/Swarm:
4 creatures = 1 creature of highest level + 1, minimum +2 damage bonus
That is different from the official one for the Swarms (explained in this answer).
I cannot find this rule on the Numenera rulebook nor the Cypher System rulebook. Is a house rule, or a failure of mine in the Intellect task to find it?