Based on prior knowledge, blood insulin levels can be used to provide insights into a person's age group. Generally, as a person ages, their blood insulin levels tend to increase. 

For the given task of predicting whether a person belongs to the senior or non-senior age group, we can analyze the relationship between the feature LBXIN (respondent's blood insulin levels) and the target variable. 

To generate the dictionary with the requested format, we need to determine the appropriate ranges of values for each target class (i.e., 'Adult' and 'Senior') and include five typical LBXIN values for each class. 

Please note that the ranges and typical values provided below are for illustrative purposes only and should be adjusted based on domain knowledge and the specific dataset being used.

```json
{
  "Adult": [5.2, 7.9, 6.4, 5.8, 6.1],
  "Senior": [7.3, 9.1, 8.6, 10.2, 8.9]
}
```

In the above dictionary, the "Adult" key represents the target class for non-senior age group, and the "Senior" key represents the target class for the senior age group. The values associated with each key are lists of float values (blood insulin levels) that are considered typical for each age group.