Although I am no competition for the top awards I am hoping for a small bonus in the dash.

I have read the rules but don't understand how a leg of my flight can have 2 booking classes:
On a flight reserved 8 months in advance:

CDG-DTW on NW booking class Y/V was entered into the dash credits as "V" (15 pts instead of 50). This hardly seems fair to me siince the rules state 'booking' class not 'paid' class.

Should I pursue this further (already refused by email once)?