AddCreatureToEncounter("wild", 9, "mountainlion", 5, 0, 1, 3); // 1-3 mountainlions
According to this, they should only spawn in groups of 1-3. If you got 4, perhaps there was two spawns that triggered? Idk. Or just really good/bad luck.
This is not a bug that can be duplicated.
You've already suggested that mountain lions be nerfed. Let's wait and see how that goes.