Based on prior knowledge, the number of grains per plant (NGL) is an important feature for determining the grain yield of soybean cultivars. Generally, a higher number of NGL would indicate a higher grain yield, while a lower number of NGL would indicate a lower grain yield.

Here is a dictionary with possible NGL values for each target class ('low' and 'high'):

```json
{
	"low": [10.2, 9.7, 8.5, 9.1, 7.8],
	"high": [15.3, 14.8, 16.7, 15.1, 16.2]
}
```

These values are just examples and can vary depending on the specific soybean cultivar and experimental conditions.