src/main/java/org/helm/notation2/parser/notation/polymer/MonomerNotationGroupElement.java
public List<Double> getValue() {
    if (this.isInterval) {
      return new ArrayList<Double>(Arrays.asList(numberOne, numberTwo));
    } else {
      return new ArrayList<Double>(Arrays.asList(numberOne));
    }

  }
public List<Double> getValue() {
    if (this.isInterval) {
      return new ArrayList<Double>(Arrays.asList(numberOne, numberTwo));
    } else {
      return new ArrayList<Double>(Arrays.asList(numberOne));
    }

  }
method to get the ratio or the interval of this group, in the case of an
interval it returns a list of two values

@return List of the values