With little frozen material inside, the air reading may respond noticeably to opening. The observation must still be interpreted with the instrument's position and the appliance's intended conditions.
What the observation tells you
This does not mean a nearly empty freezer may be allowed to warm indefinitely. Nor is adding a large warm load an immediate fix. A selected target and a brief air measurement are different kinds of information.
A useful next step
Keep measurements consistent, follow the normal setting and loading guidance, and investigate persistent unsuitable temperatures. Plan any added freezing load within the model's capacity rather than filling it impulsively.
Manuals and supporting guidance
Model-specific instructions take priority. These references support the practical principles discussed here; they do not diagnose your appliance.