While the maximum of students that you can have in one RoundTable is 150, we recommend keeping your discussions between 5 and 35 students. This will make it easier to manage, and will be less overwhelming for students to engage with everyone's ideas.
There is no maximum number of students you can have in one course.
Here are some options you might consider:
Create courses for your different groups of students.
Split the group into two RoundTables. You can do this by duplicating the original RoundTable (click the three dots, then duplicate) then sharing the new invite link with the other group.
Split the class into two groups and have half the class discuss in an Online RoundTable (written), and the other half discuss in a Live RoundTable (verbal) with the teacher. Next class, you can switch!