As far as I know, there seems to be no such feature currently implemented on MobiControl.  I recently have also personally asked Soti management team  similar question about device enrollment in Soti Snap.


However,  it might be very difficult to implement and monitor if the restriction is associated with an add-devices rule, mainly because devices can be relocated, deleted/unenrolled/re-enrolled, and also scattered everywhere in a big device tree.   No human being can track the history and sensibly decide how to adjust the device count threshold.


It seems to be much easier if the limit is associated with the maximum number of enrolled devices (of predefined device platform(s)) CURRENTLY in a device group (targeted by an add-devices rule), or in the whole subtree under such device group. This way, the count threshold can easily be mapped to number required/limited based on departments, projects, location, MobiControl administrator, or any other dimensions represented by the device group sub-tree. 


Ir would, of course, be even better if there is option to limit devices under a group/group=tree across all or some platforms (e.g. there can be at most 30  "iOS or Android" devices IN device-group A, or there can be at most 60 devices of "any" platform UNDER root-device-group B).  The solution will be perfect if there are additional global and per-group access permission controls for different web-console administrators in the All-Platforms->Security tab.


For anyone who are interested, please voice out your support here.  I believe some Soti guys active in this forum wuld  officially file a feature request if they could see strong support and heated discussions.