Just checking my understanding.
The early Carthaginian list allows up to 20% allies. These can be Numidian or Spanish.
If I go to the Numidian list because they have elephants (and I have a number of african elephant models that I want to play with!) it says that in the Numidian list I must take at least 25% cavalry and then I am allowed one elephant for each 250 points.
On the basis that it says in the blurb about allies that if the allies list has a 1+ unit then you have to take one of those before eveything else then I will have to ensure that 25% or more of the allied force is cavalry.
The question would then be can I take one elephant for each 250 points of the main army or of the allied force?
I would suggest this should be based on the main army rather than the allied force.
Otherwise on the basis of a standard 1000 point army you could never have an elephant in the allied force as that would give a maximum of 200 points of allies that would not be enough for a single ellie.