Good day: This pack include 2 Caliban unit. But only one Caliban unit is allowed. Is this a mistake? Thank you
Not really, the action pack also acts as the starter pack for SEF which is one of the sectorials in the full game, where you can take up to 4 caliban.
Bear in mind the Action Packs are made by combining two products that were released before Code One existed, the contents were tailored more to N3. Infinity also has incredibly generous proxy rules so feel free to use the second Caliban as a Jayth, Noctifer, or any other 25mm based trooper.