There is a well known formula for a single Probe calculation to determine the deployment:
Biweekly discovery toward [The number of Inventory Discovery nodes] + daily discovery toward 5 times [the number of application dependency mapping nodes] is less than or equal to 25000 (for Standard deployments) or 50000 (for Enterprise deployments). For example, 15000 inventory discovery nodes (in two weeks) and 2000 application dependency mapping nodes (every day) is a Standard deployment.
The easiest way to calculate the number of discovered nodes per a probe is by creating a report. Create a TQL query bundeled to that report showing Node and ipAddress classes. Next, filter the "ip_probename" (IP Probe Name) attribute of the ipAddress CIs to show the nodes which belong to a certain probe.