False discount value when displaying net prices

-- url of the page with the problem -- : pharmacyshop.eu
-- HikaShop version -- : 2.4.0
-- Joomla version -- : 2.5.28
-- PHP version -- : 5.3.3

Hi,

Our webshop shows all the prices in net value. I would like to set up a discount for a given product with a fixed value like:
original price: 7.80 Ft
discount: 1.80 Ft
discounted price: 6.00 Ft.

Instead of the correct values, the customer can see the next values:
Net price: (- 1.8 Ft) 6.38 Ft.

If I increase the discount by the local VAT (27%) then I can see the correct discounted net price, but the discount value is wrong in this case (2.28 Ft).

So something is not properly calculated or I misconfigured Hikashop.
- Default tax category is set up properly,
- The VAT category of the product is set to Default tax category
- The price is displayed in the original currency

What could cause this issue?

Best regards,

Daniel

That was the solution. Thank you!