Instance discovery time

So PropertySources are used to add properties to whole devices/resources. So good for items like the firmware, OS version, when the device was added to monitoring, etc. 

"Instances" have a specific meaning and are when you have monitoring check (like network interfaces or disk volumes) which would apply multiple times to one device. So for example a switch might look like this:

• Switch01 (properties for this can come from PropertySources)
  • CPU     (aka NetSNMPCPUwithCores)
  • Network Interfaces     (aka SNMP_Network_Interfaces)
    • FE0/0
    • FE0/1 ... These are multiple copies of the "Network Interfaces" check.
    • .etc

CPU would be a DataSource without any instances, while Network Interfaces is a DataSource with multiple Instances.

So Interfaces that auto-add themselves would come from the DataSource's AutoDiscovery script. So you likely need to look at the AutoDiscover script for DataSources like "SNMP_Network_Interfaces" to add properties to instances. Note that these properties will start with "auto."