Based on the given feature, "Repetition" and the task of predicting the grain yield of a soybean cultivar as either "low" or "high," I will assume that the repetition refers to the number of times the experiment or measurement was repeated using the same or different cultivars.

To analyze the relationship between the feature "Repetition" and the task, I would need access to a dataset that includes the values of "Repetition" along with the corresponding grain yield values for each soybean cultivar. 

However, since the feature "Cultivar names" is mentioned as a numeric variable, I can assume that there are different cultivar names associated with the Repetition values. Therefore, I would not be able to determine a specific range of values for the Cultivar names to generate a dictionary. 

Therefore, I will only create a dictionary for the feature "Repetition" with the given target classes of "low" and "high." Here is the dictionary formatted in markdown:

```json
{
	"low": [1.0, 2.0, 3.0, 4.0, 5.0],
	"high": [6.0, 7.0, 8.0, 9.0, 10.0]
}
```

Please keep in mind that this dictionary is created based on an assumption related to the feature "Repetition." Actual analysis and the generation of this dictionary would require access to data.