Does anyone know what these temperature readings represent?
HWMonitor and Speedfan both show them.

Sorry Richard I did not see this till today
What you are seeing are registers the system has and the software is reading. As for their accuracy, I would question that based on one of them being way out of range. Typcially, new motherboard have new type IC's in which the software maker such as Speefan must update their software to read the chips correctly or get it within a reasonable spec.
As for what you are seeing, specifically is, I dont know. The code markers for the temps do not tell me anything
Speedfan has dropdowns in its config area which allow the user to set offsets to temps and so on.. usually, if the software is updated for the motherboard/chipset it will have a correct description of what is being read.