Each brigade is made up of “unit strength markers”. Each marker represents approximately 200 men, or, in the case of artillery, a battery of about 8 guns with 50 men to operate them.

The maximum that is allowed into any one hex is 5 brigade strength points in battle line, or 10 strength points in any other formation, and up to a maximum of 3 artillery batteries and 1 commander.

The hex with the commander is just about at maximum stacking limits. It has 3 batteries, 1 commander, and 3 brigade strength points (the other brigade at the top of the picture is not in the same hex).