Based on prior knowledge, the number of stems (NLP) in soybean cultivars can be a good indicator of grain yield. A higher number of stems typically leads to a higher grain yield, while a lower number of stems generally results in a lower grain yield.

To create the dictionary, we need to consider the appropriate ranges of values for the number of stems. Let's assume that a low number of stems would range between 5 to 20, and a high number of stems would range between 30 to 50.

Here is the dictionary with typical NLP values for each target class:

```json
{
	"low": [5.2, 8.9, 12.4, 15.6, 19.3],
	"high": [31.2, 35.7, 40.1, 44.8, 49.2]
}
```

Please note that the values provided are just examples and may not represent the actual NLP values for a specific soybean cultivar.