Perhaps Temp3 the system or chipset temp. Not all MB have the same kind of sensors. That's more for you to figure out.
However, you should have 2 core temps and CPU temp, I believe. Though I'm not too sure about how the sensors on Amd side.
Try using HWmonitor
, and compare what it shows, might give you hints on some things. Also your MB utility app should show temps on certain things that you could match up.