Unable to use golden leaf discounts

[Maelael]

I want to use my golden leaf discount items to buy things but the exchange gui does not notice that the discount you selected alters the price. I would like to buy limited giftpack 23 which has a base cost of 90 leaves and i want to use a 100 leaf discount reducing the leaves to 0 but when i try to buy i still need leaves. please fix this as the discount items are timed and the pack i want is also timed