Bottom heat concentrates its contribution beneath the food. It is usually a finishing or specialised function rather than a substitute for every ordinary baking mode.
What the observation means
A dish can receive enough heat at its base while its exposed surface browns slowly. That difference does not, by itself, show that the oven's upper element has failed. The important comparison is between the selected function and the result its instructions describe. A bottom-heat symbol often contains a lower horizontal line, but check your own manual before relying on its appearance.
A useful next step
For the next normal meal, select a mode that suits the recipe and the oven's cooking chart. Do not raise the temperature sharply just to colour the surface while the base is already darkening. If the same imbalance occurs on a verified conventional setting, retain the shelf level, dish material and mode as useful assessment details.
Manuals and supporting guidance
Model-specific instructions take priority. These references support the practical principles discussed here; they do not diagnose your appliance.