Hi James
ok here goes with reference to the A330 , some failures typically slat and flap lead to an increase in VLS in this case the VLS desplayed on the PFD takes into account the actual configuration , in some other cases you have to fly the aircraft at a speed higher than VLS simply to better its handling characteristics at that point , this is your Delta VLS provided by ECAM , this speed increment is to be added to the VLS displayed on your PFD when landing conf is reached . . . . .
again QRH 2.40 as you know is where you get the formula to find the Vapp .
hope this helps
