Thanks for reaching out to the Zoom Developer Forum and Welcome !!
I am happy to help you out here.
We do not have a specific way to create meetings for a specific number of participants.
What I suggest that you can do is to add the registrants that will attend to the meeting so only the ones that are approved will be able to join
https://marketplace.zoom.us/docs/api-reference/zoom-api/methods#operation/meetingRegistrantCreate
Hope this helps
Elisa