The Values Allowed option as defined on the course record does not effect how the grade calculates in Faculty Access for the Web. The marking column grade will always calculate numerically, but if the value allowed is set to Grade, the grade will automatically post as a letter grade.  To have the letter grades appear in FAWeb, they must be manually entered as letter grades.  However, once another grade is changed, added, or deleted, the calculation will trigger again and the numeric value will return.