Generally speaking the two temperature readings will be close to each other. They magnitude of the difference between the two will depend on the incoming air temperature, the flow rate used, and the temperature of the instrument. To check the instrument temperature you can look at the variable ‘block temperature’. The outlet temperature should be closer to the block temperature in general.
Another thing to check is the head pressure. It is on the same circuit board as the inlet and outlet thermocouple. If there is any issue in the cabling on the board you will see issues in the head pressure reading.
If pressure readings are correct and the temperature readings are questionable you can replace the thermocouples. Two spare themrocouples are included in the spares kit. If you suspect incorrect readings