Boots advantage card

I was wondering if anybody has experience with this! I bought a pram from boots but my husband has decided we need a different colour! I collected £20 worth of points which I have spent already on suncream etc… I know that when you return items they deduct the points you earned….. if I’ve already spent the points does anybody know what happens? Does the value get deducted from the refund? Can’t find any information anywhere.