The introductory paragraph to the list says that it concentrates on "the army employed in Hannibal's invasion of Italy, and the aftermath at Zama." So I don't think that the (I) is intended to restrict Hannibal himself exclusively to Italy. As for Hannibal's Italian campaign, the handful of elephants that survived the march over the Alps participated only in the very first battle at the Trebia. All (or all but one) of those elephants appear to have died in the battle, and the beasts did not play any subsequent role in Hannibal's Italian campaign. Hence the limit on elephants for Hannibal in Italy.
"Experience is the teacher of all things."
~ Gaius Julius Caesar