Different positions, response times and measurement tolerances can produce different readings without either device proving that the fridge is faulty. Compare like with like before altering the appliance settings.
What the observation tells you
One sensor may have been sitting beside a cold wall while another was recently carried through a warm kitchen. Displays that refresh at different intervals can also show different moments in the same cooling cycle. Check both instruments' operating ranges and whether either has a weak battery or visible damage. Do not average an obviously unreliable result into a food-safety decision.
A useful next step
Place suitable thermometers in comparable positions according to their instructions, allow them to settle and record the conditions. If disagreement persists, use a reliable reference instrument or seek guidance. Keep perishable food appropriately chilled rather than repeatedly moving the dial to satisfy whichever reading happens to be lower.
Manuals and supporting guidance
Model-specific instructions take priority. These references support the practical principles discussed here; they do not diagnose your appliance.