Please note that Mommsen uses the AUC chronology (Ab Urbe Condita), i.e. from the founding of the City of Rome. You can use this reference table to have the B.C. dates
The position in which matters stood is shown by the anxious
carefulness, which during the ensuing Macedonian war the senate
evinced in the watching of Italy, and by the reinforcements which were
despatched from Rome to the most important colonies, to Venusia in
554, Narnia in 555, Cosa in 557, and Cales shortly before 570.
What blanks were produced by war and famine in the ranks of the
Italian population, is shown by the example of the burgesses of
Rome, whose numbers during the war had fallen almost a fourth.
The statement, accordingly, which puts the whole number of Italians
who fell in the war under Hannibal at 300,000, seems not at all
exaggerated. Of course this loss fell chiefly on the flower of the
burgesses, who in fact furnished the -elite- as well as the mass of
the combatants. How fearfully the senate in particular was thinned,
is shown by the filling up of its complement after the battle of
Cannae, when it had been reduced to 123 persons, and was with
difficulty restored to its normal state by an extraordinary nomination
of 177 senators.