Asset Scan Errors help

Okay, I am trying to make heads of the errors that I receive form Domain asset scans, and why i need clarification is, we are spread over 40+ sites in 2 countries and I really need to be sure of what we have here in regards to errors!

Bascally I am trying to determine what the errors mean, I have a machine in the office with me that is returning the "Connection to RPC server in the workstation failed" which SD+ suggests is an issue with Firewall, but the machine is actually turned off which should really get this error ""No response received from workstation. Probably the workstation might be switched off or does not exist. ""

Or are these errors not that accurate.

Hope there is an answer out there, as it will be annoying if they are all inaccurate!!

Thanks as always