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

However, without specific information on what is considered a "low" or "high" grain yield, it is challenging to define precise numeric ranges for the feature NS. In this case, we will use arbitrary cutoff points to categorize the target classes as "low" or "high" grain yield.

Based on this analysis, here is the dictionary with typical NS values for each target class:

```json
{
	"low": [2.0, 2.5, 2.8, 3.2, 3.5],
	"high": [3.9, 4.2, 4.5, 4.9, 5.2]
}
```

Please note that these values are arbitrary and may not reflect the actual relationship between NS and grain yield in the soybean cultivar.