The Body Mass Index (BMXBMI) is a measure of a person's weight in relation to their height. To determine the appropriate ranges of values for considering someone as senior or non-senior, we need to consider the typical BMI ranges associated with different age groups.

Typically, a BMI between 18.5 and 24.9 is considered normal weight for adults, regardless of age. However, since we are specifically looking at the "Senior" age group, we can consider a higher normal range. Let's consider a range of 18.5 to 26.9 for "Adult" and above 26.9 for "Senior".

Based on this analysis, the dictionary would look like this:

```json
{
    "Adult": [18.5, 20.0, 22.5, 24.0, 26.5],
    "Senior": [26.9, 28.3, 30.1, 32.6, 35.2]
}
```

Please note that these values are just examples and are not based on any actual data. The actual values may vary depending on the specific dataset used and the defined age groups for "Adult" and "Senior".