Event ID 20999 is for Command Response and isn't specific for Inventory but applies to any command. For example, the event is generated if you run the command sadmin version (executed using the run command option), or run a task to disable or enable ACC. When you execute a command on the client, ACC sends the result of that command to ePolicy Orchestrator (ePO) and generates 20999 event XML. Event ID 20999 is added to the Solidcore Client Task Log. You can verify this behavior by executing any run command client task and checking the log for Event ID 20999.