Ok this could be valid up to 20200 ft, over this altitude the "up mark" is removed from view, but it grow up proportionally to the altitude, so as far as we studied aerodynamics on books, the minimum drag speed is less than the best L/D speed, but from FMS manual the minimum drag speed over FL200 equals the FMS best holding speed which is very close to the cost index 0 economy speed and sometimes when very heavy, higher than C.I 0 speed which should be the best L/D spd...
simply curious!