A revised determination of entitlement to a supplementary welfare allowance given by an officer of a health board shall take effect as follows -
(a) where any supplementary welfare allowance will, by virtue of the revised determination be disallowed or reduced and the revised determination is given owing to the original determination having been given, or having continued in effect, by reason of any statement or representation (whether written or verbal) which was to the knowledge of the person making it false or misleading in a material respect or by reason of the wilful concealment of any material fact, it shall take effect as from the date on which the original determination took effect, but the original determination may, in the discretion of the officer of the health board, continue to apply to any period covered by the original determination to which such false or misleading statement or representation or such wilful concealment of any material fact does not relate;
(b) wher