Based on prior knowledge, the Thousand seed weight (MHG) feature can be analyzed to determine its relationship with the grain yield of the soybean cultivar. Normally, a higher MHG would indicate larger seed size, which can potentially result in higher grain yield. Therefore, it is expected that higher MHG values would correspond to a high grain yield, while lower MHG values would correspond to a low grain yield.

To generate the dictionary with the specified format, I will provide 5 typical values for each target class ('low' and 'high') based on the range of values for MHG:

```json
{
	"low": [20.5, 21.2, 19.8, 18.9, 20.1],
	"high": [28.3, 26.7, 30.1, 29.5, 27.9]
}
```

Please note that the specific values provided here are just examples and may not reflect the actual data. The actual MHG values for each target class would depend on the specific dataset and analysis conducted.