Based on prior knowledge, the number of stems (NLP) can be used as an indicator of the grain yield of a soybean cultivar. Generally, a higher number of stems would indicate a higher grain yield, while a lower number of stems would indicate a lower grain yield.

Based on this analysis, we can create a dictionary as follows:

```json
{
	"low": [1.0, 1.5, 2.0, 2.5, 3.0],
	"high": [4.0, 4.5, 5.0, 5.5, 6.0]
}
```

This dictionary provides typical values of NLP for each target class, where "low" represents cultivars with low grain yield and "high" represents cultivars with high grain yield. The values given are floats and represent possible values of NLP for each target class.