What was entered as ZFW shouldn't matter once Approach is activated because after that Vapp is not estimated but calculated. Following was a bulletin from Airbus.
GW and CG values are computed from entered ZFW and ZFWCG corrected for the predicted FOB and CG variation. When the Approach phase is activated, the characteristic speeds are recomputed using the actual weight and CG.The performance model used to compute the characteristic speeds, is accurate enough to provide speed errors of less than ± 2 kt from the certified speeds.