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
But, apart from the circumstance that the Spanish troops might arrive
in Italy with the spring either by the land route through Gaul
or by sea, the men of the three legions still remaining
from the levies of 699,(11) as well as the Italian levy sworn
to allegiance in 702,(12) could be recalled from their furlough.
Including these, the number of troops standing at the disposal
of Pompeius on the whole, without reckoning the seven legions in Spain
and those scattered in other provinces, amounted in Italy alone
to ten legions(13) or about 60,000 men, so that it was no exaggeration
at all, when Pompeius asserted that he had only to stamp
with his foot to cover the ground with armed men.
13. This number was specified by Pompeius himself (Caesar, B.C. i.
6), and it agrees with the statement that he lost in Italy about 60
cohorts or 30,000 men, and took 25,000 over to Greece (Caesar, B.C.
iii. 10).