Discovery may not be collecting the exact same model name that appears in APM. If the same model is discovered differently you can normalize models to match.
You can do this by going to Directory - List Management.
Under Normalization go to System Model Normalization
If the model, for instance, LENOVO KJH8678 does not appear on the left, add it.
Then choose the model to map it to on the right and click Map.
Check if this maps the discovered asset to the correct model.
You can review Data Normalization Rules in the Admin document: