In Gen de Armee a commander must allocate orders (roll dice) to each brigade in the force, a brigade usually consists of between two to six units with approx two to three brigades to the division. For an good size game it would have two divisions per side but it can be played using one division per side with a couple of dice rolled for the commanders.
I believe these rules to be the best Napoleonic or in my case French Revolutionary rule set out there but this is only my opinion of course. I gravitated to these rules from Gen de Brigade which are a little bit more in depth but still a good set and are aimed at one division per side on average.
So to answer your question I will be adding a couple more full size (24 figs) units to the figures above to complete this brigade.
Dave.