Based on prior knowledge and analysis of the relationship between the feature "duration" and the task of whether the client subscribes to a term deposit or not, we can create a dictionary that provides the possible values of the feature "duration" for each target class.

```json
{
    "no": [100.0, 150.0, 200.0, 250.0, 300.0],
    "yes": [350.0, 400.0, 450.0, 500.0, 550.0]
}
```

This dictionary includes 5 typical duration values for each target class, where "no" corresponds to clients who do not subscribe to a term deposit, and "yes" corresponds to clients who do subscribe to a term deposit.