Dio 68.15.1In Julian Bennett's Trajan: Optimus Princeps, the figures given are 117 days, 11,000 animals, and 4941.5 gladiatorial pairs.
Upon Trajan's return to Rome ever so many embassies came to him from various barbarians, including the Indi. And he gave spectacles on one hundred and twenty-three days, in the course of which some eleven thousand animals, both wild and tame, were slain, and ten thousand gladiators fought.
This was the largest contest of gladiators in Rome.
The event's from Trajan's Dacian campaigns are sculpted on Trajan's Column, a 100' high monument from Trajan's Forum.