A Note in our MEL states:
The VFE is displayed on the PFD according to the flap lever position.
Overspeed warning is computed accordingly to the actual flaps/slats position.
With the SFCC 2 inoperative, retraction time of the slats from CONF 1 to FLAPS ZERO may take up to 1 minute and 30 seconds. During the retraction period, make sure that the placard speeds are not exceeded, as the VFE limit on the PFD will disappear when selecting FLAPS ZERO.
Hope that explains it.