To achieve a set temperature of 900C in a furnace with a measured temperature of 909.2C and no offset option in the controller, one must account for the deviation of -9.2C. Users are encouraged to refer to the oven and controller datasheets, as well as the manuals, for potential calibration procedures. It's crucial to verify the accuracy of the temperature measuring device being used. One suggested approach is to conduct experiments to create a lookup table that correlates the desired temperature with the actual behavior of the furnace. The discussion highlights the need for practical experimentation in the absence of direct calibration options.