How can incoming air be warmer than outgoing than outgoing air

I am running a Mac Pro3,1.

Observing sense values with Tech Tool Pro 8, I see FBDIMM Riser A Incoming Air at 51.00 C and FBDIMM Riser A Outgoing Air at 45.00 C. I do not know what these values indicate, but I they look like the temperatures of incoming and outgoing closing air. What puzzles me is that the incoming air is a higher temperature than the outgoing. If the air is carrying heat away, the incoming air should be cooler than the outgoing.

I also see FBDIMM Riser B Incoming Air at 47.00 C and FBDIMM Riser B Outgoing Air at 52.00 C. These values are as I would expect.

I asked Tech Tool Pro support, and was told these values are simply reported as read from Apple hardware.

It apparently works so there seems to be no problem. Nevertheless, seeing something that seems so out of line bothers me.

Can someone who knows the engineering details please help me understand this?