It is easy to change existing value, but creating new one is much more complicated.
This is how this ResultValue object looks like:
As you see it is not only the value itself, but also a lot of different data like confidences and references to the document (region, size etc).
If you want to create value for single field, use SetValue method to the field object:
objExtractionResults.ResultsDocument.Fields.FirstOrDefault(function(x) x.FieldId.Equals("NoGroup.NoCategory.REMI.correctamount")).SetValue(new ResultsValue("Yes",nothing,1,1))
As an argument of SetValue method use the new ResultsValue object (there are a lot of constructors, use the simplest one). In my example (binary field) I use “yes” as value, nothing as ResultContentReference, and 1 for confidence levels