Depends on the time frame. The classical legion, described by Polybios, consisted of about 4500 men, 1200 velites, 1200 hastati, 1200 principes, 600 triarii and 300 equites. That is theory, in the field numbers were possibly always different. Sometimes the maniples of the hastati and principes could be raised up to about 160 instead of 120.

To the legion was always added a roughly similar number of allies (with more cavalry normally), forming the ala (wing). A normal two legion consular army consisted so of about 20000 men and formed battle order with the two legions in the centre and the two alae on the sides/wings.

The RTW/EB stacks are not made to simulate a legion or a consular army in numbers of men. No problem, use the adequate number of units.

In the second Punic war, the Romans did not raise 4 legions but different number over the years, for example about 25 legions for the year 211 BC.