eyeson allows multiple meetings and webinars live during the same time as it scales on demand in the cloud. So there is no limit for eyeson video calls and webinars during the same time.
You can also join multiple meetings and webinars e.g. on your PC in parallel with the same user at the same time, but you need to take care about your local CAM / MIC access when you do so.
Please also note that beside this you could also face limitations of your own network / internet access or working environment.
To find out more about the technical environment requirements of eyeson please read this article.