Based on prior knowledge, the number of grains per pod (NS) can be expected to have a positive relationship with the grain yield of soybean cultivars. Generally, a higher number of grains per pod would indicate a higher grain yield.

Based on this analysis, the dictionary with the requested information can be generated as follows:

```json
{
	"low": [2.5, 3.2, 2.8, 3.6, 3.1],
	"high": [4.7, 5.2, 4.6, 5.8, 5.3]
}
```

These lists contain typical values for the feature NS that can be associated with each target class ('low' and 'high').