Our software can directly handle pretty well up to 5.000 people, but you may get in trouble with a higher number of people. For Stadiums and Theaters, anima® has a Demo scene called "Tribune" that you can access from the Welcome window when you start it.
It is an Area with a particular setup (cheer animations, grid mode, and adjusted spacing between seats), we made it as an example of how the Area tool works and how quickly you can build a large number of people distributed in a regular grid of seats.
However, we recommend you take a different approach to fill up completely a football stadium with a huge amount of people (+10.000 people). You can easily generate anima® scenes with small groups of people (i.e. a line of seats or even individual actors) and then, inside 3dsMax® or Cinema4D®, create render proxies (VRayProxy, Arnold Stand-ins, CoronaProxies) directly from the anima® objects and distribute them with some scatter tool like CoronaScatter or iToo Forest.
In the following demo reels, you will find some examples of the results that can be achieved using anima®: